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#103223 - 03/09/02 11:15 AM Poor performance from stock 86 L98
86Z51 Offline
Member

Registered: 11/24/01
Posts: 1089
Loc: arizona
Maybe somebody can offer an idea of why my 86 Coupe is running so poorly: the car sat for between 1 1/2 to 2 years but was run up about once a month. Now that it is back on the road it is way down on power. It can be difficult to start but once it is running, it runs smoothly.
I'm not going to mention what I've already done to correct it so that I don't put any ideas into anyone's head. Thanks for the help.

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#103224 - 03/09/02 01:54 PM Re: Poor performance from stock 86 L98
c4c5specialist Offline
Member

Registered: 07/10/01
Posts: 1612
Loc: conn
HI there, welcome,
As for the hard start, is it cold or hot, when this occurs, or does it matter??
Do you see anything out of the exhaust??? Like smoke of any kind??
Do you smell anything when this occurs?? Like fuel, coolant, or anything else out of the ordinary??
Any codes in the system???
Are there any mods that have been done???
Has your MAF sensors relays been changed to the updated part numbers???
Please let us know what you have, and we can help.
Welcome to the c5forum family, c4c5 hammer
_________________________
c4c5 Chevrolet dealership mechanic, ASE Master Technician w/L1. COFFEE ADDICT. A persons judgement is only as good as the information they have, which should be FACT, not fiction.


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#103225 - 03/09/02 09:53 PM Re: Poor performance from stock 86 L98
86Z51 Offline
Member

Registered: 11/24/01
Posts: 1089
Loc: arizona
OK, the engine is completely stock except for a 180 degree thermostat and K&N air filter. The cast iron heads were replaced by the factory aluminum heads. The car was chasis-dynoed after replacing the heads and was initially down 20 hp but after replacing the Y pipe and main converter it picked up 10 hp over the best with the iron heads. Along with the heads, the injectors were cleaned. After getting the car back on the road after an extended hiatus, the car just didn't sound or pull like it did before. I have checked exhaust back-pressure, changed spark plugs, replaced fuel filter, replaced fuel pump (it died), run lots of injector cleaner through it, discovered that the EGR control vacuum line was melted and was getting recirculated exhaust all the time (I really thought that that would be it, but I got only a marginal improvement when I fixed it).
The car is in South Florida (cold there is less than 72 F). I plan to check that the spark plugs are correct, do a compression check, check for vacuum leaks, check fuel pressure. The car's battery is pretty old and I'm thinking about replacing it since I have seen performance drop off because of low battery voltage, but nothing like this. The car can be hard to start, like the fuel pump is not cycling when I first turn the key on. I'll crank it, and if it doesn't start, I'll stop, wait a few seconds, try again and it usually catches. The fuel return line was crimped in the vicinity of the fuel filter (don't ask how that happened) but seemed to make no difference in how the car ran. What seems odd, is that the car hardly makes any noise; it has a Borla Cat back and used to make pretty healthy noise, but is positively stealthy now. I checked the exhaust back pressure by pulling the O2 sensor and putting in a pressure gauge which I realize is a little different than the manual procedure, so I'm still a little suspicious of the exhaust. The car has 70,000 miles on it and does blow a little oil smoke on start up and acceleration, but is clean under most circumstances. I know this is a pretty long laundry list, but I have limited time to look at this thing and I was just hoping somebody might be able to give me a silver bullet that I hadn't thought of before. By the way, Barbie, it looks like you found quite the place to do your engine install.

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#103226 - 03/09/02 10:08 PM Re: Poor performance from stock 86 L98
86Z51 Offline
Member

Registered: 11/24/01
Posts: 1089
Loc: arizona
I just re-read your questions, and no, the MAF sensor relays have not been updated, and the computer used to display codes while I was driving but would disappear before I could check them out. I don't seem to be getting any codes lately, though. Keep in mind that it runs what seems completely normally (except for the starting problem) until I ask for a lot of power (or what passes for a lot of power for a 16 yr old engine - 220 rear wheel horsepower was its best). Even then, it's smooth, just puny. Mucho thanks for your help.

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#103227 - 03/10/02 11:30 AM Re: Poor performance from stock 86 L98
c4c5specialist Offline
Member

Registered: 07/10/01
Posts: 1612
Loc: conn
HI there,
Ok, what was your pressure reading, Barb may have something here, with the clogged converters??
At start up, and at 2000 rpm????
Was the PROM for the computer updated for the increased efficiency of the aluminum cylinder heads??
As for the hard starting, I would suggest that you replace the relays at a starting point, and install a fuel pressure gauge on the fuel rail, and see what pressure you have at key on, without starting the engine.
This would be first. If you have good fuel pressure, then we proceed. Meaning 35-41 psi.
Please let us know what we have, c4c5 hammer
_________________________
c4c5 Chevrolet dealership mechanic, ASE Master Technician w/L1. COFFEE ADDICT. A persons judgement is only as good as the information they have, which should be FACT, not fiction.


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#103228 - 03/10/02 08:41 PM Re: Poor performance from stock 86 L98
86Z51 Offline
Member

Registered: 11/24/01
Posts: 1089
Loc: arizona
I don't have a definite answer on the back pressure, but it would barely register on my gauge and was definitely below the shop manual value (2 PSI?). I thought that the cats were going to be the culprit, myself, although they probably have less than 10,000 miles on them. The PROM was not updated. According to my GM parts man, the E-PROM was not changed, so I didn't pursue it any further. I guess I could try pulling the the pipes off and seeing how it runs, but my neighbors sure won't like me. All of this headache seems to be related to the car sitting for so long, or at least that is my impression (may be just a coincidence, too, since when I swapped the heads, the power dropped off though not as bad as now, and that turned out to the precats clogging the main cat - good guess, Barbie!)

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#103229 - 03/14/02 07:19 AM Re: Poor performance from stock 86 L98
69MyWay Offline
Member

Registered: 03/06/02
Posts: 36
Loc: Orange Park, Florida
Barbie I agree 100% on the CATS. I have had the same problem with three C4s. Poor performance, very little volume of sound out of the mufflers, and general lazy acceleration.

I even had a cavalier once with a CAT that was less than a year old. It was built the same as the C4 cat. It broke up internally and caused me a ton of performance problems. Imagine how bad your 86 is, now imagine a 2.0 four cylinder trying to overcome a plugged exhaust pipe.

One other important thing however is the ignition timing. You may either have so much advanced timing that the knock senosor is kicking in and retarding the timing when you accelerate, or you are so retarded to begin with that it is just running weak.

You really need to put a full scanner on the car and watch the systems function. Your balancer might have slipped, and what appears to be good timing on the mark is a mile off. You will know if you put the scanner on. Set it to read knock retard, warm the car up and go for a ride. As Paul has pointed out to me in the past, there will always be some ping going on, but you want to see little to no knock retard popping up on the sensor with good quality gas and WOT under a load.

If you keep advancing the timing until you pick up knock retard, then retard it until it is on the hair edge of tripping, you are pretty close to the max street timing you can run. At that point it really does not matter what you are reading at the crank with a timing light.

Hope this helps.
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#103230 - 03/15/02 06:23 PM Re: Poor performance from stock 86 L98
86Z51 Offline
Member

Registered: 11/24/01
Posts: 1089
Loc: arizona
Thanks for the input. I guess I'm a little reluctant to conclude it's the pre cats since I just put a new Y-pipe on not that long ago for over $500. Anybody know of any good deals on front Y-pipes out there? Sorry, but I can't use the Canadian types without the cats.

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