I've got a bit of a nightmare with my 88, guys. Showed up on my doorstep and I had to give it a home, even though it's a high mileage auto. (It's my 3rd C4. I still wonder how Chevy could ever put out a vette under 300 horses and still give you eye contact... but I love 'em... and can't get used to the big butt on the 5&6s). Anyway, this one's got our expert mechanics here in Hawaii baffled. Loads up high end and especially since I changed the computer it idles like you pulled a plug wire, with a 'clack' at 1100rpm (wasn't running well before either. They thought it was a plugged cat so I eliminated them and replaced the entire exhaust system). Just can't get her to run worth a darn. Injectors check out, platinum plugs and I'm getting 9mpg.

Thanks for your input. Aloha! Pila Chiles, author, "The Secrets & Mysteries of Hawaii" 5 star Amazon

 

Is the car giving you any codes? There is something wrong if the engine is seeing that much fuel.

 

Heck, that makes more simple logical sense than anything I've heard. I'm retired and my mechanican days were before electricity so I'm still an autistic, bi-polar dsylexic when it comes to computers (but I'm larnin'!). The check engine light, after crawling to the top of the hill was the 02 sensor before, and the boys said my computer being a "12 series" should be replaced, so they did. I'm not getting any other flashing Christmas lights from the dash other than a false "low coolant" reading. They said the computer is functioning properly, and after a $1,500 exhaust system that should have cost 400 and is threatening to cost my hearing, I've determined that it wasn't a plugged cat.

Runs slightly stronger after all this expensive ridiculousness, but still bucks then loads up high end (and clacks with a miss like you're banging on a Hieneken beer tapper with a wooden spoon. It's not a rod though, nor apparently inside the engine.)

Any thoughts out of the blue would be appreciated. All the crystal ***** here in paradise are fogged over with pakalolo (if you happen to know what that is).

Aloha, and I appreciate your input~!

-Pila

 

Do you know the history on this car? IE: last tune up, oil change etc. I'd start with the basics since you're not getting any codes. Get the idle straightened out then work on things like fuel pressure, fuel filter etc. Is the throttle body gummed up that you can see?

 

I would check the throttle position sensor and the maf sensor. If the TPS is jacked way up things get ugly since the computer doesn't know what to make of that situation and it's never given me a code..... The MAF's usually give a code but anything's possible. Let me know if any of those things check out and I will ask a GM tech I know that's pretty good on this stuff what he thinks if I can catch him over the weekend. I like the above idea; pop the throttle body off and see what it looks like; you can also check and see if the idle air control valve looks nasty by pulling it out. If you have any type of service manual, now's the time to pull er out!

 

Thank you Gentlemen. Will check throttle body and position sensor, etc. Supposedly it had platinum plugs and oil change before I bought her. Two shops including a Corvette specialist said the exhaust system was plugged so I just replaced everything. Same problem, if not worse (actually better top end but it still misses with a loud "clacking", not internal engine but wouldn't sound worse if you spun a bearing and pulled a plug wire. I'll try your suggestions, Thank you!

 

Well gentlemen, I have replaced the entire exhaust system, the fuel pressure regulator (set at 45lbs, front plenum gasket was leaking significantly) and the fuel pump and my problem has worsened. Mechanics have been fiddling with it for 2 days now and it runs rough as hell all the way through the acceleration spectrum with no codes on the newly replaced computer. (Also replaced the MAF sensor at a whopping double the price). The new oil sending unit has never read properly (canister type but not "black" like another forum says it must be). Can that be tied in? Registers zero forever then 9 lbs for a while then shoots up to 35 and back and forth. Just mentioned it because the mechanics are now looking for an excuse to say the engine's junk (even though it appears electrical and is worse than when I bought it in!) They ordered a PS155 Standard (which is also not black) and didn't put it in when the saw it had already been replaced. Any Christmas ideas? I'm going broke and could use some elf magic right now. Thank you!

 

So much for them being "specialists". FIND ANOTHER SHOP. These guys are guessing at this point.

 

In other words.............they're stumped.

35 is low on the oil pressure but it could just be a bad sending unit as stated.

Have you removed and cleaned the throttle body and IAC valve? Reset the TPS voltage? Checked the timing? As mentioned, if the TPS is out of range then the ECU will not send out the correct signals.

 

The lost top end power and loading up could be related. Has anybody scanned this rig while driving? The loading up could be the knock sensor retarding timing at high rpms. Scan the rig and note the knock counts along with knock retard of the timing. You need to find the source of your noise, as it could be setting off the knock sensor and causing it to retard the ignition timing. Is this an auto or stick car? If it is an auto car, does it do it the same in nuetral and drive? (Cracked flex plate) I had a roller cam go flat on a few lobes, and the noise was enough to set the knock sensor. I chased this for quite some time before I found the cause for the knock retard. Just my .02 worth.
Steve

 

Figure out what that noise is first. If you fix that and it still runs bad, I'd guess bad injectors. I know you said they were checked, but based on what you're saying about the guys working on the car............ This is assuming the basics like compression and ignition and fuel pressure are OK.

Good Luck, Paul

 

Well gentlemen, I finally have decent acceleration for the first time, but now she's overheating and the dash display changes intensity. Before calling in the Kahunas for an exorcism I thought I'd ask your input once more. The only thing I could get out of the mechanic was "it was vacuum leaks and the timing was set at 0 so I advanced it to 6". It's been overheating ever since they changed the fuel pump and pressure regulator. Use to back off at 235 now it fluctuates then goes past 240 (and someone told me that will crack the block!). Finally hauls a little *** though!! Oil pressure never has read right (new sender but someone said you have to have a "black" one or it won't work. Had a problem like that in the early parts days. GM kept putting light sender (switches) in the guage boxes.)
Happy New Year!~ (Haoli Makahiki Hou). -Pila on the Big Island (where the volcano is ...currently under my hood).

 

You don't state whether the fans are coming on. It is possible that the shop knocked something off while working on the car. The dash changing intensity is the dash's way of trying to get your attention to the temp indication. My '89 dash will change intensity any time that a gauge indication needs attention. As far as the overheating goes, a change in ignition timing will cause it....hence masking the knock sensor retarding the timing by advancing the base timing. Check the upper radiator hose as the engine reaches 190 deg. you should feel the hose get warm as the engine temp aproaches 180-190, if it suddenly gets warm at that temp you can assume that the thermostat is good and that coolant circulation probably isn't the cause of your problem. Look for the proper diagnostic connector pins to jump with a paper clip (I think that it is a and c) to put the ecm into diagnostic mode. With the pins jumped and the key on the main fan should be running. If it isn't running, then it is time to look to see what may have been knocked off, or what fuse may have blown.
Steve

 

One other thing... during the FPR replacement, the shop probably would have had the coolant temp sensor unhooked to remove the fuel rails. Check at the front of the intake manifold right next to the coolant hoses, there should be a connector right there connected to a brass colered sensor. That is the coolant sensor, It is responsible for telling the ecm the coolant temp, that temp is also used by the ecm to switch the main fan on at 226 deg.
Steve

 

THANK YOU, Steve, for this very intelligent feedback! We'll try your suggestions tomorrow. Aloha, -Pila

 

Well, guys, after two more tows and another thousand bucks I drove her from the local Corvette specialist, Route 66 up the hill to go home and she caught fire! Hood wouldn't release (they thought it was because it was on an incline) and no one would stop with a fire extinguisher or a beer so I just had to watch her burn a nice brown spot on the hood. Total of six grand and in my pension retirement I'm little discouraged. Question is, how do you get the hood open? (Passenger side still won't release.)

To recap: Went in with engine missing and loading up. They said it was a plugged cat after charging $500 for a rebuilt ECM. Replaced entire exhaust system with Car Quest stock sh*t and it was so loud I couldn't drive (still same engine problem "loading up and cutting out"). (Car Quest uses horrid universal mufflers with Corvette bends that drone like Chinese water torturel. DON'T USE THEM). Replaced entire exhaust system again with headers, smog puller replacement and stock MidAmerica muffs. Finally got some nice bottom end... same engine problem after driving a while, loaded up, started missing. Replaced Fuel Pressure reg and pump (overheated and found they hadn't bled the system or changed the 160 stat I'd bitched about 3 times). Promised labor credit was denied at Kona Muffler, so I went back to Route 66. After second tow and checking injectors hot and cold, it was still missing like hell so he retarded timing to 3 degrees, upped TPS to 64 ...and she caught fire on the way home. I need to get the hood open and am reluctant to do it sober. Can you help with either the technology, a lawyer or a fifth of Jack Daniels? Kind regards, -Pila (Damn she was a pretty car!)

 

WOW. Sorry to hear. I read through the thread to find out that things got worse. As for opening the hood you will need a tool like THIS.

I was going to ask if they disconnected the EST wire when setting the timing? Sounds like you have a bigger problem now.

 

Yup...

You got vacuum leaks.

High mileage? If the squeeze is good in all 8 holes, pull the intake, and just clean house (carbon/oil fouling, and new gaskets).

See how many problems go away for the cost of gaskets...

 

Any updates on the damage ?