Went for an interview this morning, it's about an hours drive from here. About half way, it felt like the overdrive let go, check engine light came on. Pulled into a station to check it out.Nothing leaking everything seemed fine, itcranked back up fine, idled fine, went to give it some gas, and it just bogged out, when it did try to go, it just pops and sputters. I finally got it going, but I could mash the gas and it acted like it was running out of gas,but I can floor it, and it runs like a scalded ape, when I let off the gas just a little, it starts topop and sputteragain like it's running out of gas. Didn't think I was going to get it home.

When Imove the connection at the throttle position sensor, it seems to rev just a little and it acts better for a little while.. I'm letting it cool at the moment, then I'm gonna go start checking things.

If anyone has any input, I would sure love to hear it.

 

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What I've found so far.... Fuel pressure is fine, it hangs around 32 psi, jumps to around 38 psiwhen I snap the throttle. Pulled the codes, 32 & 33.

32 is the egr valve, I already know thatit's bad, besides, it wouldn't cause the symptoms I'm having. 33 is mass airflow sensor,...that's possible, but not probable, I just replaced it about three months ago

I suspected the throttle position sensor, butIhad replaced it around the same time as the MAF sensor, but I went ahead and replaced it again anyway. I set the voltage on the new one at 0.54 volts, cranked the motor, same thing, nothing had changed, idled good, but as soon as I opened the throttle it would bog as if it wasn't getting any fuel.

Well, while I was standing there scratching my butt, wondering what the heck could be wrong, I reached over and put a little pressure on the connector on the TPS, the engine jumped to around 1800 rpm's. While it was running like that, I checked the voltage on the TPS again, it had jumped to 0.97 volts. I adjusted it back down to 0.54 volts while it was running, and the idle dropped back down to 700 rpm. I can wiggle the wires at the connector and hear the rpm's bouncing around, so I think I have a bad TPS connector. Going to try to find another connector tomorrow, may be able to find one in a salvage yard. I'll be sure and let y'all know how it goes.

So, to sum up my day, what was suppose to be a nice cruse in the Vette, turned into a freakin nightmare about sixty miles from home.

Cheers

 

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You probablyhave a badTPS. Voltage should be rock solid at idle around 1/2 volt, no fluctuation. Also check your VREF to your TPS and MAF, should be close to 5 v, 4.87 is acceptable. Doubt you have a connector problem, havent seen many of those fail if any. Could be a broken wire, check your ground to TPS plugged in by backprobe while plugged in on the voltage scale to chassis ground with key on. Absolutely no more than .1 volt on ground side. Watch your analog scale on the VOM while sweeping the throttle and look for glitches or voltage drops. Should be a smooth transition from idle to WOT. Was your MAF a rebuild or new? I've had bad burnoff relays that have not affected MAF, since the burnoff relay just is used to clean the hot wire inside the MAF after running engine. MAke sure you have good power and ground to relay as I described on the TPS.

 

Thanks for your input Mech, it's greatly appreciated.

This is the second tps I've bought in the past three months. I checked both the old and the new onewith an ohm meter before I installed them, and I checked the voltage transition from idle to wot after it was installed, and both testshad asmooth transition with no glitches or dead spots. I can wiggle the wires where it goes into the connector and the rpm's go nuts, it even died a couple of times. I've got a feeling it's got a broke wire inside the connector. I'll check the tps ground to chassis ground and see what it looks like.

The MAF was a rebuilt Bosch,I can hear the burn-off relay click about 5 seconds after I shut the engine off.

 

BTW...would the tps have anything to do with the overdrive dropping out, both problems started at the same time.

 

It's possible. You say "dropped out", do you mean it quit pulling or did the trans go out of lockup? Mid 80's GM used a vacuum transducer to contol lockup and in the early 90's went to ECM control lockup. Your TPS problem now sounds like a broken wire or a cold joint in the connector. I think the connector pins have an indexing mark on the plastic part that surrounds the pin, so watch for that when you try to find a used one.

 

Torque converter lockup released...

EDIT: Beat to the punch again[:@]

 

I did a little research in my wiring diagrams and your ECM does control overdrive lockup based on inputs from TPS, overdrive pressure soenoid or 4th gear solenoid. THe ECM looks for your trans to be in 4th gear with the TPS around 1- 2 volts and the brake switch off to go into lockup. So I think you are on the right track because erractic TPS readings will confuse the ECM. Pins C12 and C13 on the ECM are the signal return from the TPS (Dk Blue wire). Try a wiggle test on signal return and VREF to see if you get any fluctuations in voltage.