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Adding a boost guage is a good Idea. Do not make any modifications (IE: the wideband) until it is running normally. May cause more headaches during troubleshooting.

The momentary surge on decel ( throttle lift ) reminds me of a bad speed sensor on the automatic cars. The Auto cars apply slight throttle when coming to a stop to prevent stalling. The manual cars don't have that feature. Since you replaced the speed sensor, have you had any speedometer issues? If you can get a scantool (drb3) to see what the mixture is doing at that moment? Also, if you can get an analog ohm meter, test your TPS through full range. Go slow and watch for needle jumps. It should vary smoothly. A digital meter will not show this due to its sample rate.

Good Luck
 

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85 New Yorker 2.2 T1, multiple red 1991 Spirit R/T's, lots of bits and pieces
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Discussion Starter · #22 ·
The speedo seems good. If I were to guess based on performance, the mixture is wrong most of the time. It smells rich. Once in a while (usually after fiddling with stuff around the TPS), it drives great for a little while, very responsive, smooth, and powerful. In other words, it feels like it reads the TPS right sometimes and wrong most of the time.
 

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The computer relies on the TPS to provide immediate input of throttle. Kinda like the old fashioned accelerator pump in a carburetor. If not correct, it will cause a lean condition on throttle open. Closing throttle makes the mixture rich momentarily. The MAP fine tunes mixture at a slower rate.
If you was to put gauges on it, I'd recommend fuel pressure, vacuum/boost and O2. That is what I had in my minivan. Gauges will provide real time data. Monitoring via a DRB/scantool works, but with a slight delay.
What rpm does it idle at? with it running, if you disconnect the booster or pvc hose from the intake and leave open, without touching throttle, what rpm does it stabilize at? about 3000? Don't forget to reconnect hoses!

good luck.
 

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Did u test the harness to the sensors itself. All my Tbi cars had cooked iac/iat wiring like this. No codes just hesitation and ran like crap.

Hood Motor vehicle Vehicle Car Automotive design


Also try unplugging the speed sensor. My Dodge 600 was stalling/random idle issues due to a shorted sensor.
 

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Discussion Starter · #25 ·
I'm trying to do little things at a time, since it's an intermittent problem with strange nuances. So, here's what I've done. I swapped out another MAP/Bar set, and nothing changed. (Previously, a known good set made the car basically not drive at all.)

I attempted to remove the O2 sensor. It's a new Bosch sensor, but then again I have two new TPS's that don't work at all. I noticed that keeping a very exact throttle during acceleration had a specific behavior: Smooth torque for a second, then misfiring for a second, then smooth torque for the duration. That made me think it was incorrectly adjusting to the mixture it was seeing go out the pipe. Unfortunately, it's very stuck. I may try that tomorrow. I have an almost new Mopar sensor I can try.

I haven't yet tried unplugging the speed sensor. I discovered that it does in fact happen across all speeds. I also haven't done the vacuum idle RPM check as described above.

Here's the interesting thing. I change the TPS yet again! The buck/surge when closing the throttle plate is there, but now I have smooth solid acceleration across the RPM range. The exhaust eye-burn seems to be gone, too. Oh, and get this. This TPS reads 1.6v when the throttle is closed! It's a Holley (stock) from out of a 2.5 Turbo. shrugs This TPS is way wrong, but the computer likes it, and it drives great.

I've still got to try driving with the speed sensor unhooked, and I also still want to install the boost gauge.

I had yet another theory about all the madness. I notice something very strange about the temp gauge. As soon as the temp starts to rise into the normal operating range, the tach starts to work. I assume that has to do with the cluster. However, when the engine is showing full operating temperature, the buck/surge problem is either minimal or gone. It's almost never at full operating temp...or at least is rarely SHOWS that. The previous owner had simply removed the thermostat. I installed a 185 degree thermostat. I expected to see the needle stay up higher, but it doesn't. I was under the impression that the coolant temperature sensor only controls the fan and the block temperature sensor only shows a readout on the cluster, and the O2 sensor gives it the feedback whether to choke or not. Could it be that one of these sensors is bad and causing it to stay rich? I did once see the "temperature stayed too low for too long" code before installing a thermostat, so I know the car is capable of determining that, but I haven't seen it ever since installing the thermostat.
 

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I'm trying to do little things at a time, since it's an intermittent problem with strange nuances. So, here's what I've done. I swapped out another MAP/Bar set, and nothing changed. (Previously, a known good set made the car basically not drive at all.)

I attempted to remove the O2 sensor. It's a new Bosch sensor, but then again I have two new TPS's that don't work at all. I noticed that keeping a very exact throttle during acceleration had a specific behavior: Smooth torque for a second, then misfiring for a second, then smooth torque for the duration. That made me think it was incorrectly adjusting to the mixture it was seeing go out the pipe. Unfortunately, it's very stuck. I may try that tomorrow. I have an almost new Mopar sensor I can try.

I haven't yet tried unplugging the speed sensor. I discovered that it does in fact happen across all speeds. I also haven't done the vacuum idle RPM check as described above.

Here's the interesting thing. I change the TPS yet again! The buck/surge when closing the throttle plate is there, but now I have smooth solid acceleration across the RPM range. The exhaust eye-burn seems to be gone, too. Oh, and get this. This TPS reads 1.6v when the throttle is closed! It's a Holley (stock) from out of a 2.5 Turbo. shrugs This TPS is way wrong, but the computer likes it, and it drives great.

I've still got to try driving with the speed sensor unhooked, and I also still want to install the boost gauge.

I had yet another theory about all the madness. I notice something very strange about the temp gauge. As soon as the temp starts to rise into the normal operating range, the tach starts to work. I assume that has to do with the cluster. However, when the engine is showing full operating temperature, the buck/surge problem is either minimal or gone. It's almost never at full operating temp...or at least is rarely SHOWS that. The previous owner had simply removed the thermostat. I installed a 185 degree thermostat. I expected to see the needle stay up higher, but it doesn't. I was under the impression that the coolant temperature sensor only controls the fan and the block temperature sensor only shows a readout on the cluster, and the O2 sensor gives it the feedback whether to choke or not. Could it be that one of these sensors is bad and causing it to stay rich? I did once see the "temperature stayed too low for too long" code before installing a thermostat, so I know the car is capable of determining that, but I haven't seen it ever since installing the thermostat.
Try swapping the temp sensor. I tried 4 of them till mine ran right. The bad ones had the connector spin side to side if u twisted it.
 

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The temp sensor (two pin) is used in the fuel mixture calculation as well as fan control. If you unplug it, it goes into a limp in mode. The single pin only runs the gauge in the cluster.

I believe all the intercooled engines also had a charge temp sensor to measure air temp in the intake. This could also affect mixture.
 

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Discussion Starter · #30 ·
I feel like I'm writing a bad comic about a demon-possessed car.

Disconnecting the speed sensor doesn't seem to have an effect, other than getting a code.

I replaced the O2 sensor. The old one seemed good, but a faulty O2 sensor would have made sense. shrug I tested the old coolant temp sensor. At full operating temperature, it should read between 100 and 1000 ohms. It read 984. After much delay cooling and warming back up, I replaced it with a new one, which also reads about the same. I deleted the BOV, and that solved the inconsistent power problem. (It seems they're all bad. Meh, I'll probably just leave it off. I'm sure the big ol' Garrett can eat the boost just fine.) Keeping in mind, the problem I'm trying to solve is still the power surge when the throttle plate closes, so even a faulty BOV sorta kinda could make sense if it's letting the boost out when the throttle opens and the turbo is spooling up, then closing the throttle closes the BOV and suddenly there's boost hitting the intake....but alas, that does not seem to be the cause either.

So....I went for a test-drive after changing the (apparently good) O2 sensor with another O2 sensor, and it threw a fireball out the intake! Fortunately, the radiator spontaneously started spraying coolant to put out the fire. :poop:

The key dance gave 12, 53, 24, 24, 55. I did it twice to make sure, and both times it gave code 24 twice, which is bad TPS.

Got it back into the garage and replaced some EXPLODED vacuum lines and fixed the coolant leak. I couldn't find anything else wrong, so I went to do several test drives, and it's been running perfectly. 🤬
 

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I feel like I'm writing a bad comic about a demon-possessed car.

Disconnecting the speed sensor doesn't seem to have an effect, other than getting a code.

I replaced the O2 sensor. The old one seemed good, but a faulty O2 sensor would have made sense. shrug I tested the old coolant temp sensor. At full operating temperature, it should read between 100 and 1000 ohms. It read 984. After much delay cooling and warming back up, I replaced it with a new one, which also reads about the same. I deleted the BOV, and that solved the inconsistent power problem. (It seems they're all bad. Meh, I'll probably just leave it off. I'm sure the big ol' Garrett can eat the boost just fine.) Keeping in mind, the problem I'm trying to solve is still the power surge when the throttle plate closes, so even a faulty BOV sorta kinda could make sense if it's letting the boost out when the throttle opens and the turbo is spooling up, then closing the throttle closes the BOV and suddenly there's boost hitting the intake....but alas, that does not seem to be the cause either.

So....I went for a test-drive after changing the (apparently good) O2 sensor with another O2 sensor, and it threw a fireball out the intake! Fortunately, the radiator spontaneously started spraying coolant to put out the fire. :poop:

The key dance gave 12, 53, 24, 24, 55. I did it twice to make sure, and both times it gave code 24 twice, which is bad TPS.

Got it back into the garage and replaced some EXPLODED vacuum lines and fixed the coolant leak. I couldn't find anything else wrong, so I went to do several test drives, and it's been running perfectly. 🤬
Leaky injectors? Pull the rail with injectors and turn key see if any are dripping. U said it was rich....
 

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Discussion Starter · #34 ·
Ah, gotcha. I don't think that's what's happening. I'm sorry I neglected to mention the misfiring, stutter, and rattle that preceded the bang by a fraction of a second. I think the computer's interpretation of timing went waaay off for some reason. Everything on this car has been a mystery. The bigger mystery is why it runs flawlessly now. It's consistently responsive with smooth boost gain and easy control at low speeds. The buck/surge problem hasn't come back since the explosion either.
 

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Ah, gotcha. I don't think that's what's happening. I'm sorry I neglected to mention the misfiring, stutter, and rattle that preceded the bang by a fraction of a second. I think the computer's interpretation of timing went waaay off for some reason. Everything on this car has been a mystery. The bigger mystery is why it runs flawlessly now. It's consistently responsive with smooth boost gain and easy control at low speeds. The buck/surge problem hasn't come back since the explosion either.
Timing on a T3 is based off the crank sensor and the knock sensor can pull timing.

My T3 car stalled when pressing in the clutch that's how I found all the bolts holding the trans in were missing making it separate between shifts but a $400 Sprit RT isn't gonna be perfect.

See if the problem comes back in the next few days pull plugs to see if it's too rich or lean check coil pack for cracks etc.
 

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Discussion Starter · #37 ·
Have I already said that I hate this car? I hate this car! I love this car! Okay, I hate it too...but just in sheer raw performance, this thing is unreal! I've been taking as many side trips as I can, and it's still driving very very well. (It has a momentary hesitation at low throttle, but it hasn't bucked once. Also about one in twenty WOT pulls doesn't feel like it boosts at all. That might be a weak wastegate, boost hunching, not sure. These are subtle, ignorable, and probably just minor out-of-spec issues.) Apparently the car just needed to be flame seared like a steak one time.

It pisses me off to not know what the problem was, but if I were to hazard a guess, it was probably a blocked/cracked/leaking vacuum line that I hadn't detected before. I'll update if the problem comes back. shrug
 

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Discussion Starter · #38 ·
Turbo-III is just not good.

The buck/surge came back, and power disappeared again. Now it also occasionally stutters and stalls out, feeling a lot like the ignition system is repeatedly turning on and off. I did get another code 24, and THIS time I got a 3v reading at closed throttle, which means it wasn't making good contact with the TPS. Sure enough, the NEW connector stopped making contact with the TPS, no matter what angle I held it at. I also tested the Holley TPS I had in there (the one stolen from the 8v Spirit), and surprise! It was bad! It reads zero ohms at closed throttle. I took a TPS that tested good and I soldered that motherfucker in. Now there's no TPS code, but the buck/surge is constantly there, and power is poor.

Also I seem to have broken 3rd gear. It doesn't feel like there's anything to engage there, and it just pops back into neutral when I try. 1,2,4,5,R all work.

Screw this car. I'm selling it to try to get back my losses. Three Spirit R/T's, $10k dumped in, not one good running 16v example.
 

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Turbo-III is just not good.

The buck/surge came back, and power disappeared again. Now it also occasionally stutters and stalls out, feeling a lot like the ignition system is repeatedly turning on and off. I did get another code 24, and THIS time I got a 3v reading at closed throttle, which means it wasn't making good contact with the TPS. Sure enough, the NEW connector stopped making contact with the TPS, no matter what angle I held it at. I also tested the Holley TPS I had in there (the one stolen from the 8v Spirit), and surprise! It was bad! It reads zero ohms at closed throttle. I took a TPS that tested good and I soldered that motherfucker in. Now there's no TPS code, but the buck/surge is constantly there, and power is poor.

Also I seem to have broken 3rd gear. It doesn't feel like there's anything to engage there, and it just pops back into neutral when I try. 1,2,4,5,R all work.

Screw this car. I'm selling it to try to get back my losses. Three Spirit R/T's, $10k dumped in, not one good running 16v example.
Sounds like the harness is jacked up or SBEC dying. 3rd gear issue could be just a loose shifter bushing.

If u wanna keep going spend $300 on microsquirt or just do what Donovan did and swap it to 8v.

I got rid of mine because I was scared of the expensive parts that could break on it.
 

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Discussion Starter · #40 ·
Two harnesses and three SBEC-2's? I actually already replaced the bushings. It felt like it kicked the shifter back when shifting into 3rd. Leave it to me to break an A568 in light daily driving...

I could easily do the 8v swap again (and the transmission at the same time). The 8v Spirit is running like a champ. But that's a complete mission failure. I went into this to get a DOHC setup. If I had any idea ahead of time how bad these cars are, I would have just gone with a Neon or another Altima.
 
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