I got a 93 auto 74k miles not to long ago. unfortunatly it's been giving me some problems...

Car runs fine cold, but after warming up the idle surges. It's not too bad with the A/C off, but if you turn it on you'd swear someone was trying to drive off in it. also, while driving (normally around 45-55 mph, when shifts into O/D) the car will sometime kick/jolt, sometimes pretty violently. other times I will just get short a loss of engine power under acceleration. a few days ago, though, i was driving around 45 and it completly killed on me. I myself am no mechanic, but i have mechically inclined friends/family members that would love to help me out with this one(they want to drive it too!). But no ones been able to narrow this one down yet. any advice on what to check/how to check would be greatly appreciated!

changed out the fuel filter also, didn't help.

 

you didnt mention if your getting any codes?????????????? you should be. could be any number of things. i would start looking for a vacume leak and check the spark plug wires for grounding

 

For vacuum leaks they are usually more pronounced when the ECM is in open loop (exhaust temp <600*) and are less likely noticed in closed loop. Use the old fuel pressure guage taped to the windshield trick. Notice what the pressure is while driving and when this happens. Could be weak fuel pump or opti/ICM. Have you done any work on it lately that might have caused a problem? If the SES light is on check there first.

 

After you go thru all the fuel checks and electrical, and probably find no codes, you probably are going to wind up at the opti. Perform all your basic tests and checks this is only proper procedure before you replace the opti.

You have classic symptoms some as I had myself. Bucks and kicks in high gear with acceleration, worse when hot, idle might wander or stubble and tack might jump up when engine RPM goes down, and need to down shift to get any power to get the RPMs up and reduce loading on engine. It was like Groundhog day every day. In the morning good, afternoon worse, and start again next day. Best of luck.

 

I am having a similar problem as described in this thread, http://forums.corvetteforum.com/show....php?t=1452199. After encountering several dead ends based upon advice given to me, I gave up chasing ghosts in my car's engine and took it to the local Chevy dealer. I watched as a couple of techs starting chasing the same ghosts I was in pursuit of. They ascertained that the new TP sensor was good as was the PCM and EBTCM. The 5 Vdc reference signal was present at the TPS connector. That pretty well leaves the TPS interface module, located next to the heater blower, as the culprit. The FMS fault logic tree for Code 22 bears that out too. My problem started out as an erratic idle. Then I put on the new TP sensor and immediately got the Service ASR and SES lights along with a smooth idle that ran at 1000 to 1200 rpm and a code 22 (TPS voltage too low). With these conditions the car would upshift very hard from gear to gear at about 3200 rpm due to the ASR being disabled when the PCM reverted to its default mode. Today the tech should be replacing the interface module, hopefully clearing any codes allowing him to relearn the EBTCM with the new TPS voltages. (I have a 1994 Vette that uses a NON-ADJUSTABLE TP sensor.) Good luck. Personally I'd let a professional mechanic who has a Tech 1 or Tech 2 scan tool check out your car's problems. Just my opinion.

UPDATE: The current problem described above has been solved. The TPS was installed incorrectly by me and then the tech during his troubleshooting. The TPS is non-adjustable. There is a spring-loaded, plastic slotted device inside the sensor that mates up to the throttle open/close tang. If the sensor is not mated up correctly to this tang coming out of the TB, then the TBS will not register any voltage to the PCM or EBTCM. Once the TPS was installed correctly, the error codes were cleared and the tech was able to relearn the EBTCM with the new TPS voltages using his Tech 2 scan tool.

 

thanks for all the suggestions. i plan on checking the codes tonight after work. hopefully that will lead me to find the problem.

 

I disagree. The similar sounding problems I was having with my 95 (but missing and stuttering sounded worse than described here) NEVER created any codes. It seems that these engines can drive quite horribly before sending a code.

 

My initial problem was an erratic idle after the car was driven about 20 miles allowing the engine to be "hot". Then the idle would jump erratically from about 650 rpm to 1200 or more rpm. I had NO codes or DID lights of any kind.

 

well, not suprisingly, she didn't throw any codes, but i did find this:



I'm pretty sure the one in red is the TP sensor by looking in the chiltons, but the connection directly under it (circled in green) has visibily damaged casing. the clips holding it in place are broken. It is easily movable by hand. also a little more info. the previous owner had the opti done earlier this year, and he also installed a new PROM.

I don't have a multimeter, but a plan on getting one soon, well, very soon now.

 

Your correct the red circle is the TP sensor. The other (green circle) is the IAC (idle speed control motor. The connector shell does seems to be in bad shape but it can still make good electrical connections. I would not think the IAC would cause your symptoms. Your idle might be bad, or not (driven) adjusted by the PCM and be stationary. I would get a replacement connector before you take that one off. The dealer has those parts.

Just wondering if this problem just popped up or do you think it can be related to a new chip. Sometimes the engine has to be set up to the new chip, just a thought. Did the new opti by any chance get wet? Charge on.

 

the opti hasn't gotten wet since i've had it. what has happened before that i couldn't tell you.

It has been pretty much doing this from day one, and the more I look at it, the more i'm thinking it could be the chip. I had talked to a few people before and they pretty much steered me away from that idea. luckily the previous owner was nice enough to give me the old chip, and all of the changed out opti hardware, too. it's to late today to fool with it though, and i have plans for tomorrow, but a may have a few mintutes to swap the chip out.