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Discussion Starter · #1 ·
Just the other day I had Turbo Fever and picked up a '89 Voyager 2.5T w/ Automatic. It has 190,000 miles, I am second owner. Drove it home yesterday 6 hours from Denver to home in New Mexico. On the way home I noticed it seemed very flat on power, it can get to 55, 65, and 75 fine, just does not get there quickly. Mileage was good, 20-22mpg on way home, it is hilly, two mountain passes, and averaging about 65-70 mph. Also last year it passed the Denver emissions test where they run it on a dynometer and conduct emissions analysis, and passed fine.

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So today I went through and checked verified the following items:
  • Ignition timing - tested and verified at 12 degrees with timing light
  • Fuel pressure - 50lbs idle, 55 when revved up
  • Cam timing - verified at 0 on crank mark and cam sprocket at hole
  • Installed new cap/rotor/wires/plugs - plugs gapped at .40
  • Vacuum - 14-15 at idle
  • Fresh motor oil / fresh air filter
  • All intake duct/tubing is free from any debris/clogs
  • Checked air intake duct after turbo, no deposits of carbon/oil, assume seals are good on the turbo
  • Coolant was just flushed, nothing abnormal with coolant, no pressure in the system from cylinders
  • Compression test yielded 100-110 on all 4 cylinders
  • Cat in not clogged / verified by taking apart exhaust
  • PCV valve properly works
If you watch the video, I start down in first gear. Give it full throttle and at about 5K it will drop back to 4.5K and not fully rev out to 5.5, and 'surges'. Power feels very flat, and gets flatter as it hits second.


Also noticed when I take off the oil cap, I can feel and hear air coming from the valve cover.

Why will it not fully rev out in first, and seems low on power? What am I not seeing?
 

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1)Checking your problem in the driveway at idle or no load higher RPM will probably not reveal the issue since that is not when the issue occurs.
2)Your engine vacuum is low at 14/15" HG @ idle which usually indicates a Cam Timing issue.
We have encountered this issue numerous times on the site, one tooth off and...

3)You need to tape a fuel pressure gauge and vacuum/pressure gauge (tee'd into the FPR line) to the windshield and go for a ride (with a helper) and see what fuel pressure is reading when the problem occurs.
3A) You can also "deadhead" the pump to see if it is capable of providing fuel under all operating conditions.
Connect your fuel pressure gauge, start the car, momentarily pinch off the fuel return line.
Pressure should rise Instantly to 80-100 PSI.
If it does not, be sure there are no collapsed rubber lines, restrictions and if OK, replace the pump and strainer.
*MPFI maintains static pressure at the injector tip under all operating conditions, it is a combination of push (pressure) and pull (engine vacuum).
Static Rail Pressure (Key On Engine Off or engine idling with the FPR hose disconnected) = 53 - 57 PSI.
Engine Running W/FPR Connected, Rail Pressure will drop 1 PSI for every 2" HG applied to the FPR.
IE: Static = 55 PSI, start the engine and 18" HG is applied to the FPR, rail pressure will drop to 46 PSI, these numbers change constantly as you are on and off the throttle but static is always maintained at the injector tip.
When in boost, rail pressure should increase 1 PSI for every 1 lb. of boost.
IE: Static = 55 PSI, @ 12 lbs. of boost rail pressure should be at 67 PSI.

4)You could also have a problem with Detonation/Knock Retard", if the detonation sensor is seeing knock the controller will pull timing until the knock stops, you will probably not here the knock.
You need a scanner to view knock retard and total spark advance.
This happened to me a few years ago, me and my Son went out with the scan tool looking for info for another issue, under WOT the car would not go above 60 MPH, it basically just stayed at that speed with the pedal to the floor.
We switched to look at knock retard, total spark advance was at 0 with knock detected in #2 cylinder.
The issue was an "Ash" fouled spark plug, replaced the plug and the detonation issue was gone.
Fuel pressure and knock are related, if you are lean at higher RPM's, knock follows.

5)Check Map Sensor Calibration
The Map Sensor is the "Dominant Fuel Control Sensor" on the car, problems may be present but do not meet the criteria to set a code.
5A)You will want to connect a DVOM to the Map Sensor Signal and Signal Return Lines by backprobing the connector.
(Voltage translates to an actual pressure)
Then tee a Vacuum/Pressure gauge into the line between the Baro Solenoid and Map Sensor, run the meter into the passenger compartment and tape the gauge to the windshield, when the problem occurs be sure that Map Voltage = Actual Pressure (Manifold Vacuum) and that pressure to the Map is correct.
5B)When you first connect your meter before starting the car, turn the key on, read the voltage, this is the Barometric Pressure Reading, it should equal actual Barometric Pressure in your area.
 

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Discussion Starter · #3 ·
NAJ,

Thanks for the fine points to check -

1. In the video you can see it is in low, accelerating

2. Yes, the vacuum is a bit 'low' at 14-15, but also I am at 5800-6000 ft above sea level. At this altitude this will make a engine normally running 18+ to be 2-3 lower. Cam timing - 🤦‍♂️🤦‍♂️. This gets me every time, I made same mistake with 'Reba'. Took a second look cam this morning and is one tooth advanced - 🤦‍♂️ - I need to set it back one tooth.

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3. I did 'deadhead' the pump - 85psi. I do not have any hoses that I could tape the gage to the windshield.

4. Plugs are new - gapped at .40, no carbon buildup on any plugs removed

5. Have not checked MAP calibration, but it was going to be next on my list. I will check voltage after I change the cam timing.
 

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Discussion Starter · #5 · (Edited)
So, my second post where I was second guessing my cam timing, I was wrong. The cam timing was right from the beginning.

I did check my MAP sensor, and it is good, calibration is good - .83V @ 15-16 and as I revved engine it instantly responded.

Here is a better video of what I call 'surging'. This is starting in Drive, and it is in first gear, WOT. It will not shift until I slightly let off, but it will not rev out and shift at WOT.

(The oil pressure gage seems low, and as it revves out, seems to get lower. Some reason the sender as the pressure goes up, it sends the signal to show lower on the gage. I did verify oil pressure with a separate gage, and it is at 30-32 at idle, and goes up to 60 when revved)

 

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Drive it back up and I'll take it off your hands ;).

The guy selling it was being weird when I tried to buy it. That's a damned nice van. I hope you can work out the issues. If you ever do want to get rid of it drop me a line! :)

FWIW - I bought a turbo shadow recently with other issues as well, but it "surged" similarly. There was a vacuum line with a small hole in it that I replaced that resolved it. I believe going to the wastegate. I will try to dig up a video of it so you can compare. Will be a while as I'm at work.
 

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Sounds like over boost shutdown this time.

Running a direct line from vacuum to the wastegate could confirm.

As mentioned above, leaky vacuum lines can lead to overboosting.

Thanks
Randy
 
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The engine @ 190K in a heavy vehicle has lived a hard life. The compression readings and low HG suggest maybe it might be pretty tired. Acknowledging the altitude will make readings lower. The engine sounds REALLY lazy to me. Noticed it has a boost gauge. Does this engine have ANY modifications done to it, like say low buck Mopar conical valve spring change, exhaust system, SMEC custom calibrations, replacement fuel injectors? Was the tranny ever rebuilt? When you are checking/setting cam timing, are you using TDC mark on converter or timing marks at crank snout? I ask because I've seen rebuilt converters with covers welded back on in wrong location resulting in TDC marks not really TDC. Did you try driving vehicle with exhaust disconnected? Cat might not be blocked, but downstream of it could be.
 

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According to Chrysler you only need 100 PSI minimum on compression, my car was only 115.
Font Material property Parallel Rectangle Number

If you want to verify if the engine is the issue you need compression numbers and cylinder leakdown test numbers.

Also, I will state it again, Knock Retard, I had no idea how much power you can/will lose until it happened to me.
 

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Discussion Starter · #11 ·
The engine @ 190K in a heavy vehicle has lived a hard life. The compression readings and low HG suggest maybe it might be pretty tired. Acknowledging the altitude will make readings lower. The engine sounds REALLY lazy to me. Noticed it has a boost gauge. Does this engine have ANY modifications done to it, like say low buck Mopar conical valve spring change, exhaust system, SMEC custom calibrations, replacement fuel injectors? Was the tranny ever rebuilt? When you are checking/setting cam timing, are you using TDC mark on converter or timing marks at crank snout? I ask because I've seen rebuilt converters with covers welded back on in wrong location resulting in TDC marks not really TDC. Did you try driving vehicle with exhaust disconnected? Cat might not be blocked, but downstream of it could be.
I agree 100%, it feels very lazy above 3K, it pulls hard from dead stop, squealing tires and pulling good until 3 -3.5K, then falls flat. I put boost gage on to see how turbo was performing.

This was first owned by grandpa, then it moved onto his grandkids, which they just drove it.

  • No modifications at all, they just drove it and changed oil
  • It has a reman SMEC, date code of '03 from Mopar
  • Water pump was replaced in last couple of years
  • Valvetrain, exhaust, SMEC, and injectors are all stock
  • Tranny has never been touched, it is pretty loose
When I checked the timing, I used the mark on the converter, but I also made sure the dot and the line matched on snout and idler pulley. I did set it back one tooth, and ran like crap, only had 10" of vacuum, so I set it forward again. Just to confirm, the dot and line at crank side line up, and the converter line matches at 0 degree mark.

I did notice the converter was a bit rattly, so I removed the exhaust. Still performed the same with exhaust removed. Emissions converter is not an issue. Put exhaust back on.

According to Chrysler you only need 100 PSI minimum on compression, my car was only 115.
View attachment 281258
If you want to verify if the engine is the issue you need compression numbers and cylinder leakdown test numbers.

Also, I will state it again, Knock Retard, I had no idea how much power you can/will lose until it happened to me.
I have done the compression, 100-110 on all. I understand it is at minimum spec, and I expected this with the mileage. Have not done a leak=down test, it is one of the items I want to check next along with all of my hoses.

Knock retard, how does the engine respond when it goes into knock retard? I know what the TD's feel like when they go into over-boost, immediately shutting down, pretty harsh IMO.
 

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I agree 100%, it feels very lazy above 3K, it pulls hard from dead stop, squealing tires and pulling good until 3 -3.5K, then falls flat. I put boost gage on to see how turbo was performing.

This was first owned by grandpa, then it moved onto his grandkids, which they just drove it.

  • No modifications at all, they just drove it and changed oil
  • It has a reman SMEC, date code of '03 from Mopar
  • Water pump was replaced in last couple of years
  • Valvetrain, exhaust, SMEC, and injectors are all stock
  • Tranny has never been touched, it is pretty loose
When I checked the timing, I used the mark on the converter, but I also made sure the dot and the line matched on snout and idler pulley. I did set it back one tooth, and ran like crap, only had 10" of vacuum, so I set it forward again. Just to confirm, the dot and line at crank side line up, and the converter line matches at 0 degree mark.

I did notice the converter was a bit rattly, so I removed the exhaust. Still performed the same with exhaust removed. Emissions converter is not an issue. Put exhaust back on.



I have done the compression, 100-110 on all. I understand it is at minimum spec, and I expected this with the mileage. Have not done a leak=down test, it is one of the items I want to check next along with all of my hoses.

Knock retard, how does the engine respond when it goes into knock retard? I know what the TD's feel like when they go into over-boost, immediately shutting down, pretty harsh IMO.
I have a solution.
 

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Discussion Starter · #13 ·
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“Dear heavenly uh…spirit. Thank you for providing us with the direct port nitrous…uh…injection, 4 core intercoolers, ball bearing turbos, and um…titanium valve springs. Thank you.”
 
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While living in HOT San Antonio, TX years ago, I had a TII 87 Shelby Z that spent it's whole life there. It sort of did the same thing this van is doing. I changed EVERYTHING including the kitchen sink.
It would drive out of boost fine, but wouldn't rev past 16-17 PSI, then 15, 14, 13, 12, 11, etc. Turned out the valve springs had lost so much spring pressure that when in boost, the back pressure in the exhaust port was just blowing the exhaust valves open! All the springs lost huge amounts of closed and open pressure. Closed pressure was like half what it was supposed to be! Very possible that the heat conditions the car lived it it's whole life, killed those springs. When I went to compress springs out with K-D tool, I immediately knew the springs were toast.
That same car the distributor rotor decided to carbon track to the dist. shaft anytime there was a heavier load placed on secondary ignition system. Had to look far up the rotor shaft hole with a flashlight to see the carbon tracking. That one took a while to find/diagnose too, but seconds to fix.
NOS, nobody I know that's really a true gearhead says "NOS" it's NO2 or nitrous.. Only people that think they're gearheads says NOS. Jeff Foxworthy could have said that. You know your a gearhead wannabe if you say NOS not NO2. Complete fail on movies part on that one. Had another older than me friend that called NO2 "Nitrix", because well he just didn't know any better... He wasn't the sharpest knife in the rack. After me and friends correcting him like 1000 times, he finally got it right (lol)!
 

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Discussion Starter · #15 ·
While living in HOT San Antonio, TX years ago, I had a TII 87 Shelby Z that spent it's whole life there. It sort of did the same thing this van is doing. I changed EVERYTHING including the kitchen sink.
It would drive out of boost fine, but wouldn't rev past 16-17 PSI, then 15, 14, 13, 12, 11, etc. Turned out the valve springs had lost so much spring pressure that when in boost, the back pressure in the exhaust port was just blowing the exhaust valves open! All the springs lost huge amounts of closed and open pressure. Closed pressure was like half what it was supposed to be! Very possible that the heat conditions the car lived it it's whole life, killed those springs. When I went to compress springs out with K-D tool, I immediately knew the springs were toast.
That same car the distributor rotor decided to carbon track to the dist. shaft anytime there was a heavier load placed on secondary ignition system. Had to look far up the rotor shaft hole with a flashlight to see the carbon tracking. That one took a while to find/diagnose too, but seconds to fix.
NOS, nobody I know that's really a true gearhead says "NOS" it's NO2 or nitrous.. Only people that think they're gearheads says NOS. Jeff Foxworthy could have said that. You know your a gearhead wannabe if you say NOS not NO2. Complete fail on movies part on that one. Had another older than me friend that called NO2 "Nitrix", because well he just didn't know any better... He wasn't the sharpest knife in the rack. After me and friends correcting him like 1000 times, he finally got it right (lol)!
These are the stories I like to hear, situations you would never dream of happening! Never heard of valve springs weakening, definitely believe it can happen over time. I do get alot of air coming from the valve cover cap at idle. To me this seems abnormal.

I avoid any movie revolving around cars, and the F&F series drives me up the wall! Or Gas Monkey Garage, I know there are a few others, cannot stand to watch them. I do love the UK Top Gear - Jeremy was pretty good car host.
 

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These are the stories I like to hear, situations you would never dream of happening! Never heard of valve springs weakening, definitely believe it can happen over time. I do get alot of air coming from the valve cover cap at idle. To me this seems abnormal.

I avoid any movie revolving around cars, and the F&F series drives me up the wall! Or Gas Monkey Garage, I know there are a few others, cannot stand to watch them. I do love the UK Top Gear - Jeremy was pretty good car host.
Was working on a 2015 F250 6.2 and a valve Spring did this...
 

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Was this found in 2.2/2.5's? Or was this offered in MP book?
Yeah they were replacement "performance" springs for the 2.2/2.5. In reality they were half a set of springs for the small block LA Mopar engines.
That is like the MP engine mounts. They were rejects from the production pieces because the durometer hardness in the isolator was too high. Marketing... got to love it, lets sell our rejects as an upgrade to the performance crowd.
 

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Knock retard, how does the engine respond when it goes into knock retard? I know what the TD's feel like when they go into over-boost, immediately shutting down, pretty harsh IMO.
The car just falls on its face, no power, there is nothing violent about knock retard like there is with overboost shutdown.
When the knock sensor detects knock the engine controller will pull ignition timing on the cylinder(s) that has knock detected until the knock stops.
My Son and I went for a ride with his scanner (Snap-On MT2500), I do not remember exactly what we were looking for, however, I did take notes of sensor values at idle and after heat soak, so...???

With my foot to the floor in 3rd gear the car would not go over 60 MPH, it just stayed there at 60 MPH, like you were running into an extremely hard wind and you just could not go any faster, we tried 2-3 times with the same result.
(When racing I used to hit the traps in 3rd gear at 6100 RPM's/@88 MPH).
I said to him, bring up the knock retard and total spark advance screen, there we saw knock detected on cylinder 2 and total spark advance was 6 degrees BTDC @ WOT, when everything is OK total spark advance at WOT was 27-30 Degrees BTDC.
The issue was an "ash" fouled spark plug in #2 cylinder (been a problem for awhile, I usually just replace it every 6 month's.). See top row, 3rd pic to the right.
I replaced the plug and we went out again, this time with no knock retard/power problems.

Knock (Detonation) is caused by two things, excessive heat and/or excessive pressure (they are related).
Excessive heat in the cylinder(s) causes the remaining A/F mixture to ignite after normal combustion starts to take place, when this happens it is not a controlled burn and you have two (or more) colliding flame fronts which rattles the cylinder walls.
Detonation can be caused by low octane fuel (octane is the gasolines ability to resist detonation), lean A/F mixture, advanced ignition timing, deposits on the spark plug/top of pistons/valves, incorrect spark plug heat range, inefficient cooling system/deposits in the water jacket, inop EGR system (if equipped).
 
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