Hi, Im new to the Forum, this is my second post :seeya:
I recently bought an 86E TPI and its got an interesting set of issues, especially with idle. Id like some opinions and input to start planning a repair route please. Its got a freshly rebuilt motor and trans, AIR pump delete, EGR is connected directly to the plenum(that right?), some hoses are plugged with blots and screws(dislike), its less than perfect I want to fix and restore it, versus watch it rot away.
On start up, the idle drops to 400/500RPM then goes up to 1200RPM, then the idle lowers to and alternates between 600 and 900 RPM. It never stays constant. Its stalling under a minute after start up, and it will stall once the idle drops if I rev it while its in P. Also stalls sometimes when shifting into gear(from R to D). I tried changing out the fuel pump with a new one, but then it would not start. I changed the plugs and wires but to no avail. Any help would be appreciated! This car has potential and Im more a body man than I mechanic, but I love wrenching and getting dirty so Im not afraid to get into it! Want this C4 to actually look and run smoothly like I believe a Vette should :thumbsup3:
Code 42 is E.S.T
When you went thru your timing I assume you disconnected the wire?... this will give you the code until you plug it back in. I would check that connector. If the connection is not a good one you will get the code
Yes. Car was off, I unplugged that wire connector. Turned car on, shot timing, adjusted to 6 degrees, rechecked TPS at .545 volts, checked out ok, turned car off, reconnected wire, disconnected battery for 1 minute. Did I miss another wire or connector?
To test your EST connection your timing should advance up to about 15-16 degrees when you plug the EST connection back together. If your timing doesn't advance then I suspect you have a bad module causing that code to set. If it's the original module and your engine has a lot of miles on it I suggest changing the module based on mileage alone. They don't last forever you know.
Sounds like you did disconnect the right wire. TBTR makes a good point in regards to plugging it in and seeing if your timing advances.
FYI- I use white out my timing tabs and the mark for 6 degrees BTDC, makes it real easy when using a timing light.
I don't think its your ESC module, that would be a code 43
Alright so... Disconnected battery, reconnected it, unplugged timing bypass wire, started car, timing read at 6 degrees but notices it skips up to 7 degrees sometimes too. Plugged wire back in while car is still running, timing holds steady at 6 degrees. Idle is still loping. Turn off car. Start at up and timing is advanced quite a ways up there. Unplug wire while car is running, idle drops, as does timing. Timing is at 6 degrees. Computer is no longer throwing any codes.
Your timing should advance to 15-16 degrees every time you plug your EST wire back on and should go back to 6 degrees every time you unplug your EST wire.
Started this morning, idle was super low, 380-480RPM, took about 15 seconds for idle to increase to normal 600-900 RPM range. Installed new cap, rotor, coil, and ignition module. Car starts faster(didn't want to start after I got home from the store. Started, then died out immediately. ????), but seems idle is very poor on cold starts, is a little better after being warmed up. Once going, everything is fine aside from the same loping idle and what I swear is a random misfire at any given speed.that I just cant seem to figure out. Also still a slight hesitation from when flooring the pedal to the butt dyno feeling any feedback. Not sure if that's a symptom? So that leaves me to check the IAC valve, MAF sensor, and O2 sensor... And perhaps a defective ECM as a last resort.
On a GOOD day, my idle is usually in a pattern like below:
---------____--------------------------------____--------
It will go from a nice 780RPM, drop to 590-640RPM, slowly work its way back up to 730RPM, then top off at 780RPM again for a minute, then repeat.
Over the 23 years I have owned my '82 I had to replace 4 computers because the drivers that controlled the IAC motors intermittently failed and caused a very erratic idle. But the failed drivers never set a hard code. So you could have a computer glitch that is causing your problems.
I believe 85-89 all use the 165 ecm. As long as it was use with the same type of transmission as yours.
Autoparts stores do sell the ecm's for around $80
Hey guys i just followed the thread and i cant help but throw this in there...
I have an '85 myself and it has its own set of problems similar to this....
-the idle will not remain steady or evn close to it. (400-1600) in p/n
- there is a check engine light but wen i pull codes it reads 12.... So idk to make of that
- under heavy acceleration i can head a very audible squeal like a belt or pully sliping...
- there is smoke and a trans leak (doubt is related to other symptoms)
- digital instrumentation acts up occationaly
- where the taletall switches are (mpg, coolant temp, oil pres. Switches) if i leave it on "coolant temp" it switches back to voltage and that switch by itself has no "off" position it reads voltage in that position.
If it lopes then it could have an aftermarket cam in it. You could measure the valve lift of an intake valve (if you have a dial indicator). If I recall the stock lift is around .425" so if you have much more than that you probably do have an aftermarket cam.
Did you ever get the car to idle without dying and surging? Looked through the whole thread and Im not seeing an end result. Just wondering if you found a solution and didnt post afterwards or if you never resolved the stall portion of the issue. Thanks...
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Related Threads
?
?
?
?
?
Chevy Corvette Forum
669.9K posts
43.7K members
Since 2006
A forum community dedicated to Chevy Corvette owners and enthusiasts. Come join the discussion about performance, modifications, racing, restoration, classifieds, troubleshooting, maintenance, and more!