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high rpm misfire 4000 rpm wall

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7K views 50 replies 7 participants last post by  mark monte 
#1 ·
Hey guys ive been lurking on the site for a few weeks now researching about my 1988 turbo 2.2 sundance (auto). I bought the car a few weeks ago not running. I replaced the head and got it running pretty decent, but cant get rid of the 4000 rpm misfire. It feels like a rev limiter, but only around WOT. Part throttle will go to redline, but does have a minor sputter here and there. the same thing happens at WOT in park as well.

Now to make it easier to diagnose I will write what I have checked..

First off I have verified no vaccum leaks. Around 18" idle in park and 15-16" in drive.

I am getting one code that pretty much happens with the misifre.. code 41. My voltage dosent change though, the check engine light will come on with the 4000 rpm misifre/wall.

I have checked the timing multiple times, cam timing is spot on with the distributor parallel to the block. timing belt is a little on the tight side but not too tight.

I have teed in another boost guage in between the map sensor vacuum line. The guage reads 18" vacuum idle but only 3 psi during boost while the main guage reads around 7 psi. Is that normal?

I have checked fuel pressure. I can not remember the exact PSI as it has been a few days, but was around high 40's psi idle with regulator vacuum connected, above 50psi with it disconnected, during boost it increased a little as well. Fuel pressure does not dip or change during the misfire.

I check the map sensor voltage and that was in spec.

Spark plug gap is at 36. no damage to plug wires. distributor cap, rotor, disk, wires, plugs are all new. verified strong spark (blue).

Thats everything so far. What do you guys think? This is the first car that has ever had me this stumped LOL.
 
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#2 ·
First off, don't splice anything into the MAP vac line. This should be a pristine connection. Couple things to check, put a fresh set of spark plugs in and take it for a drive. You'll be prepared to stop the car right when it misfires. Pop the hood and pull the plugs. Take pictures of them to post up here if your not sure of what you are looking for.

Second thing, your fuel pressure. Try to be more specific about the actual readings. Are we to assume you have a stock ECU?

I'm thinking that this is fuel related all the way so actual plug condition and FP readings will help a lot.
 
#3 ·
1)I have teed in another boost guage in between the map sensor vacuum line. The guage reads 18" vacuum idle but only 3 psi during boost while the main gauge reads around 7 psi. Is that normal?

2)I checked the map sensor voltage and that was in spec.

3)I have checked fuel pressure. I can not remember the exact PSI as it has been a few days, but was around high 40's psi idle with regulator vacuum connected, above 50psi with it disconnected, during boost it increased a little as well. Fuel pressure does not dip or change during the misfire.
Welcome To TD!!!

I see a problem already if your diagnostics are accurate.

1)No.
Vacuum/Pressure need to be the same at all components.
If Map vacuum/pressure is not equal to actual manifold pressure under ALL operating conditions then you have a problem in the Map Pneumatic System that must be corrected)
If the Map is only seeing 3 lbs of boost and you are actually at 7 lbs of boost the controller will not give you enough fuel (by increasing injector pulse width) and you will be Lean.
If you are Lean enough to cause Detonation then the controller will Retard Spark Advance until the Detonation stops.
When Spark Advance is Retarded the car will have absolutely no power and will not go any faster no matter how hard you depress the throttle.

2)Map Voltage and Pressure need to be checked when the problem is present.
CHECKING MAP SENSOR VACUUM/PRESSURE/VOLTAGE.
http://www.turbododge.com/forums/f4/f14/344296-code-13-diagnostics.html

3)As already stated you need to check fuel pressure under all operating conditions and post EXACT numbers.
CHECKING FUEL PRESSURE
http://www.turbododge.com/forums/f4/f14/358339-checking-fuel-pressure-84-93-turbo.html

Follow the diagnostics in the two links and post back your exact results, base readings and readings @ 4000 RPM's when the problem is present.

 
#4 ·
Since you have conflicting boost readings, and this only happens at WOT, is there any chance you are hitting over boost shutdown?? Is the engine pulling hard just before your misfire??

This will cause what might feel like a misfire when boost exceeds the max allowable of approx. 14.7, but it normally sets a code 45.

If there is any chance you are over boosting, the best thing to do is attach a dedicated vacuum hose directly from the waste gate actuator to the intake. This will give approx. 7-8 PSI only and bypasses all possible boost control devices.

Other than that, Naj is the best Chrysler diagnostician in captivity, so follow all his diagnostic procedures exactly.

Welcome!!

Thanks
Randy
 
#5 ·
Since you have conflicting boost readings, and this only happens at WOT, is there any chance you are hitting over boost shutdown?? Is the engine pulling hard just before your misfire??

This will cause what might feel like a misfire when boost exceeds the max allowable of approx. 14.7, but it normally sets a code 45.

If there is any chance you are over boosting, the best thing to do is attach a dedicated vacuum hose directly from the waste gate actuator to the intake. This will give approx. 7-8 PSI only and bypasses all possible boost control devices.

Welcome!!

Thanks
Randy
+1 and Good Point and Glad you brought it up.
I was thinking Overboost Shutdown but did not post that because of the pressure readings he said he had, but...
I was also going to ask if the Code 41(Field Circuit Not Switching Properly) is correct as opposed to a Code 45.
If the Code 41 is correct you may have two separate issues or a Ground Issue.
Be sure your Main Controller Ground from the Fuel Injector Harness Connector (2 wires) to the Fuel Rail Mounting Bolt at Rear of Engine is...
Connected/Clean/Tight

One more question...
What exactly happens during the misfire?
1)Car just will not go any faster?
2)Feels like a "jerking" motion/sensation as if the engine is turning off/on, off/on until you release the throttle?
3)Vehicle backfires through the intake or exhaust?
 
#6 ·
Hey guys, thanks for all the suggestions. I recorded the fuel pressure. With engine off key on I have 47psi. Engine running around 43 psi. Engine running with vacuum removed I have 53 psi. I took the fuel filter off and blew through it, didn't feel restricted. The filter looks very recent, fuel pump looked new as well.

I took the plugs out and took pics. In neutral I floored the engine until it hit the 4000 rpm "rev limiter" and immediately shut it off and removed the plugs. Probably not to good for the turbo lol.
 
#8 ·
You need to test/diagnose when the problem occurs and once more...
Revving the engine to 4K with no load is going to cause major internal damage when a piston goes through the block.
 
#10 ·
Exhaust makes no difference, will do the same with open downpipe.

I rechecked fuel pressure at wot 4000 rpm during the misfires at 7psi and it sits at 58 psi.

I changed the fuel filter since I had it off anyway. No change.

I checked tps voltage. 1.04v closed and 3.90v wide open with no dead spots. I'll check the map volthe soon. Thanks
 
#11 ·
I tested the map sensor. It's voltage is correct for all ranges I tested.

I did make a mistake, the cars original guage is way off. Using my aftermarket guage, I am only making 3 psi of boost. Same boost level if I run straight manifold vacuum to the wastegate. With the wastegate vacuum removed it makes 14 psi. I cannot figure this thing out.
 
#13 ·
You're doing a good job of checking and eliminating things step by step.

Occasionally a weak valve spring or springs act like this.'

Sometimes work better when the engine is cold, but weaken as soon as they get warm.

Thanks
Randy
 
#14 ·
Found out something that makes this issue a little more interesting. The misfire only happens during WOT in neutral amd when the trans is in first gear. Does not happen when in 2nd gear at higher speeds. This is blowing my mind lol. Is there a speed sensor could be doing this?
 
#16 ·
is there anyway you can borrow a scanner that you can use to data log?
or get a boostbutton cable and hook the diag conn to your car and do you own data log.

it sounds like maybe knock is pulling the timing or there is a sensor fault that just isnt trowing a code.

This will help a lot if you can make a data sheet when it happens.

SCI-USB Cable - BoostButton.com

then log with
mpscan
https://sites.google.com/site/mpsuite/
 
#20 ·
Any chance you can borrow another SMEC, or distributor for diagnosing?
You no doubt have a very unusual problem, not in the code list.

The 1st gear thing might, or might not, be a direct clue.

A few years ago I bought a chipped SMEC from una and it worked fine normal driving around town, but when I floored it, it just stumbled at around 4000 RPM. In my case I noticed black smoke when it was stumbling, apparently overfuelling electronically.

With back to back SMEC swaps the problem came and went, but no codes etc.

If I would have bought it this way it could have been very hard to figure out.

As you bought this car not running, you don't know if it had this problem before, so this adds another level of unknown, what the previous owner/mechanic might have done.

Can you check your injectors and SMEC numbers, a T-II SMEC can cause problems on a T-I, not necessarily exactly like this, but as an example of possible mismatch.

When floored, these electronics go into an over fuel condition, so if it had say T-II injectors with a T-1 SMEC, that could be another possibility.

Also, Hall effects and wiring can cause intermittent/unusual problems that don't always set a code, so trying known good parts can be a real time and $$ saver. Sometimes gently wiggling the wires/connector can induce erratic running.

Again Good Luck!!

Thanks
Randy
 
#21 · (Edited)
I may be on to something... there looks to be a speedo cable and a vss beside it. I disconnected the connector and took it for a drive. The speedo still works and the trans shifts the same, what is the sensor actually doing?

But now with it disconnected the 4200 rev limiter happens at every speed now as long as I'm at WOT. Coincidence?
 
#22 ·
Signal to SMEC that the car is moving.

Mostly for idle speed when slowing to a stop and reporting mileage to the SMEC to catch people who disconnect the speedo cable, or reset the odo for warranty reasons.

Nothing to do with speedo or trans in your case.

Speedo is cable, trans is hydraulic, not electronic, in your case..

Keep at it!!

Thanks
Randy
 
#23 ·
I plugged the speed sensor back up and it's doing it in every gear now so it was a coincidence. I used a spark tester from the coil to the distributor cap. It gets blue spark then just stops sparking at 4200 rpms. Is there anything else I should test or just buy a coil?
 
#24 ·
It pains me to see folks buying parts in hope it fixes an unusual problem.

Our coils are among the best and although I've heard they occasionally fail, I've never had one go. They normally just stop entirely. Not have a blue spark, then stop at 4200 RPM, then working again below 4200 RPM??

HEP's and or distributors on the other hand can cause unusual problems.

Same thing, but much, much less common with SMECS.

Too bad you can't borrow a distributor or SMEC to try, lots of guys have spares.

Any 1986 and newer Turbo distributor works. Parts store distributors are often problematic but not this problem.

Is the car starting, running and driving fine other than hitting a 4200 RPM wall??

Thanks
Randy
 
#25 ·
I bought a coil, no change. I checked voltage at the hep. 9v at both + connectors. Low resistance to ground. With the engine running at the signal wire I'm getting 5v at one connector and 3v at the other. Is that strange to so low and different from one another? Using my test light it pulses and dosent stop even when the breakup happens.
 
#27 ·
I'm just thinking out loud here, sometimes I run a jumper wire from the battery to the ignition coil to energize the fuel pump directly to check pressure or drain a tank. This by passes the ASD and I can hear the pump buzzing.

I wouldn't recommend starting the engine and going for a drive to see if by passing the ASD had any effect on the problem ...

The ASD is a safety feature and driving with it by passed would be as dangerous as driving with your seat belt unbuckled.

I wonder if anyone has ever driven a car with the ASD bypassed??

Thanks
Randy
 
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