I have a '87 iroc with a newly rebuilt engine that runs like poo. I have come to the end of my options here and can't figure it out. I am ready to have a profesional look under the hood . It isn't stock, and certainly won't pass emissions. Does anyone recomend any garages or shops that could handle this in the Michigan area? I am running out of drivable weather here, please help.

 

Hello. One place you might want to try is:

Performance Automotive.
901 E Michigan Ave
Jackson, MI 49201
(517) 783-2627

Heard some good things from various people. Never been there myself though. I know of some good places around by me, but its a bit far. Hope this lead helps!



------------------
1987 Trans am GTA
5.7 liter TPI / 700R4
Aus 9-bolt + 3.70 gear

 

I could take a look at it for you, scan it and diagnose it for a reasonable fee.



------------------
Mike L.


1987 IROC Z 5.7 TPI A4 3.27 Borg-Warner
four wheel disc

Mods:[i] 2300-2500 Stall Converter, Shift Kit(GM parts), TPI Specialties Stage 3 PROM, Modified Airbox w/ K&N's, homemade cold air, Relocated MAT sensor, Gutted MAF, 160* thermostat, MSD 6A, Accel 8mm Wires, bypassed TB coolant, Flowmaster 3 chamber single 3" in/out muffler,cutout. 3" MAC mandrel intermediate, custom dual !cat Y-pipe. airfoil, ported plenum. !smog, few others I forgot...???

**BOYCOTT LAPEER DRAGWAY**

 

I had the same problem,does your rockers knock,if they do that could cause your car to smoke and produce no power.

 

I'm not smoking at all, nor burning oil. Can that validate the condition of my long block?

 

We can start by asking what you had, and what you have now, and define "poo" please. Do you have a scan tool?

 

As suggested by afgun, whats in the car? Still TPI i'm assuming, if the mods are extremely radical your going to need some custom chip tuning. Taking it to any garage locally isn't going to be able to figure it out and will more than likely be a waste of time and money...

 

'poo' means about 2/3 of the milage and 2/3 of the horsepower I got when I bought the car. Then it had the stock L98, with a 160` thermo, a disconnected A.I.R. belt, a rhino high flow cat and 3" cat back exuast. It started to consume oil like crazy and fouling the plugs, not to mention overheating while not going faster than 15 mph. I took it to a dealer and they said shattered piston rings after giving it a compresion test. I ordered a stock jasper replacement l98 and droped it in myself. No problem at all, it started first try. When I put in the new engine I also installed a set of flow-tech(holley) ceramic coated headers and ditched my cat. I also removed the A.I.R. system completely, added an airfoil for the TB, and switched to the specified 195` thermo. I put the engine through the most thourough break in procedure I could find and stayed out of the throttle for the first 500 miles. Now my engine is broken in, not consuming oil, not overheating, and not producing the power or milage I expected. No codes are stored in the computer, so I decide to buy an auto x-ray to take a closer look at what is going on in the ecm. With the timing set at a specified 6` BTDC I am getting up to 15` of knock retard at WOT. My tool is also not showing open loop at WOT. To add to my confusion, it also tells me that my park/neutral switch is working backwords(ie. when it is in gear it says it isn't and visa versa). At this point I am starting to loose faith in my auto x-ray and my diagnosing skills. This is where this thread comes into play, I have given up and am ready to have a profesional look at it. If any of you guys have any ideas of what could be going wrong I would be glad to hear them, but really I would just like suggestions on where to have it looked at in the michigan area. Thanks again fellas.

*I forgot to mention that I had a chance to take the old long block apart and the dealer was wrong, my lower end was in fine condition. It turned out to be the valves that were causing the problem to begin with. They were almost all different colors.

[This message has been edited by Remondi2 (edited October 10, 2001).]

 

anyone????

 

Well, your new engine's heads and cam could have a huge influence on the power and mileage. Unless you got a replacement L98 longblock, you're going to need some serious chip tuning.

I'd start by verifying that the timing mark is indeed at TDC. That way you can rule out timing problems relating to your knock. Also, have you verified your fuel pressure?

Have you tried running premium fuel to check your knock problem? You could also have something like a loose rocker. Shame, but those quickie rebuilds are just that...

You definitely need some scan data. The p/n switch I think I've seen reversed on some scantools too, so I wouldn't worry about that just yet.

You need to log your scans. Does the auto-xray have a serial connection or anything like that? It would be interesting to see your commanded timing vs. when your engine knocks.

 

Unless jasper gave me the shaft, I should have a standard issue l98, I specificly said thats what I wanted. I would be interested to see which year of the l98 cams was included in my engine though. We checked the timing mark when we re-installed the distributer, but that is a good thing to double check. Fuel pressure checks out, I have a gauge on my fuel rail. I tried running premium, and it definatly changed how the engine sounded and behaved, but still very weak and still had the same degree of knock. I haven't checked for any loose rockers, what is the procedure for that any-who. Also, what would I be looking for with the commanded timing vs. knock, I can visually compare it, but I don't have a serial cable.
Thanks For your response afgun

 

Loose rockers will make a clattering noise. They're pretty easy to notice if you pop the valve covers. Sounds like your problem lies elsewhere though.

What you'll see is knock counts going up, and a number of retarded timing degrees. Check that out and try to make a plot of things.

The knock-caused timing reduction is likely what's costing most of your power.

Since your car is fairly close to stock, a visit to a GM garage might yield some clues as well.