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90 Eagle Talon delayed throttle response

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doebelj1

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Discussion starter · #1 ·
I recently had to replace my turbo and exhaust header due to some shaft play. About 500 miles into a rebuilt engine the car would start to violently shake under boost pressure. Turns out my turbo was completely shot and the shaking from it destroyed my header. I got a rebuild kit and sent it out to be balanced. After replacing both the header and turbo the car starts up and idles okay but the throttle response is quite delayed. Before replacing the turbo the throttle response seemed fine, and the car boosts alright.

I went through and cleaned out the throttle body, which was quite gunked up (I think from the turbo seals letting oil slip into the intake). Tried again and it's still lagging. There's no CEL being thrown. I also re-calibrated the ignition timing, which seemed to help a little, but not much. Did a boost leak test and couldn't find anything. My base timing is also spot on, and I'm not sure if this would make a ton of difference in throttle response but my PTU is practically brand new. I checked the gap on my plugs, .027... any ideas as to what may be causing this?
 
Discussion starter · #3 ·
I haven't checked any of the fuel delivery system, though it sounds like the pump is working and the rail is getting fuel. I did take off the intake and that was caked with oil too. Plus it turns out my knock sensor is bad, which I'm not sure what that would do. On top of THAT, my PTU plug seems to be acting up. The Unit itself is good, but the plug has some damage to the terminals. When the plug gets touched while the car is running, the rpms fluctuate, it's definitely not a good connection.
 
#4 ·
definitely fix the knock sensor, I know when it's not working right the timing will retard and richen the fuel mixture to protect the engine IIRC.
 
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#5 ·
When the turbo "blew" did it dump oil? If so check your intercooler, it may have a lot of oil in it.




P.S. Like others said, replace that knock sensor, if it's giving a lot of phantom knock it will hurt performance quite badly.
 
#7 ·
Maybe see if unplugging the maf changes anything. A bad knock sensor and even a bad coolant temp sensor can cause the symptoms also.
 
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Discussion starter · #8 ·
The turbo definitely dumped oil throughout the system. The intake and throttle body were soaked with it. Cleaned those out. Got a new knock sensor, and replaced the PTU with a used one that seems to check out good. Went underneath and did some electrical clean up. Seems that the guy who owned it before me put in a new ECU and didn't insulate the wires correctly.

The throttle delay has gone away slightly, but the engine is still misfiring quite a bit. I checked for spark and there is intermittent spark. The rail is getting fuel, the injectors are working, replaced the coils. The coil pack itself checked out okay. And as I said above the PTU is newly replaced. I checked the alternator by unplugging the battery, and the car shuts off almost immediately. Could a bad alternator cause misfire?
 
#9 ·
CAS going out could also cause this problem. When mine started to fail it gave me similar issues, stuttering and sketchy idle, but it was intermittent and it would sometimes throw a code, then the code would go away after a minute. It was weird
 
Discussion starter · #10 ·
The CAS tested out fine. Replaced the alternator and got a little more juice out of the engine but it's still not running properly. It still misfires and spits and sputters when driving; it has no power. No boost leaks, all electrical systems seem to be in order, I have a new ECU coming in tomorrow but if this doesn't work I'm completely stumped. What am I missing!?
 
#11 ·
BISHILVR metioned MAF - Misfires, spits and sputtering sound like MAF. These cars are not happy when the MAF is messed up. Could be the MAF sensor itself or a bad connector. I'd try swapping one of those out.

Other than that ... fuel ... you say you have fuel at the rail ... do you know at what psi? Are you able to put a gauge on it?
 
Discussion starter · #12 ·
Turns out it was actually the wiring going to the O2 sensor. It was split open at a part and was grounding out. My CAS sensor happened to be 180* out as well... I reset the ignition timing and the car runs pretty good now. However, there is still a very small misfire.

When I hooked up the timing light it would miss every now and again, not too often, but you can hear it. Coils are new, PTU new, ECU is good (bought a new one and didn't effect anything), CAS is good, plugs are NGK 7es's gapped to .028. I'm lost on this one. I don't feel anything, and tested before, but would a boost leak cause a misfire??
 
Discussion starter · #13 ·
Update: I did a boost leak test and can't find anything, though it definitely is starting to run like a boost leak. I can't hear anything or feel any air coming out but the system will only hold 2 lbs. I checked the throttle body, intake piping, inner cooler piping, turbo housing, backside and sides of intake manifold, and BPV. I can't feel any exhaust leak, but for good measure I tightened all the header bolts, which seemed to be okay.

I drove it today and slowly but surely it started sputtering when getting up to boost pressure. It was doing 15+ yesterday but now struggles to get 8 psi. It idles wonderfully, but it drives poorly. I believe the MAF is okay, it doesn't throw a code but I'll check it tomorrow.
 
Discussion starter · #14 ·
Sorry for the triple post, but I forgot to mention that after pulling it in the driveway after a quick test drive (problems still ensuing) the header was glowing red in some parts. I didn't put two and two together but when I checked my plugs the other day, the tips were white, and the rings were black. Which I think means my car is running lean and hot (obviously hot from the header). Would running lean be an airflow or fuel problem? And how do you check the MAF?
 
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doebelj1
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