87 GT running rich. (Page 1/1) mountainman AUG 23, 11:04 PM 87 GT, 5 spd. 130,000 miles. No EGR. I bought this car last year at copart so I don't know its history. Ran horrible, pig rich. You couldn't stand behind the car it was so bad. So I bought a set of cheap injectors from Rockauto. Installed injectors, tune-up, new 02, etc. Ran much better. Drivable. But not perfect, it still runs rich. If I reset the computer and attach my Snap-on scanner the car starts and runs as expected. But within a minute or two the O2 sensor goes all the way up to .95v or so. Integratr starts at 128 as expected, BLM 128. As soon as closed loop happens the Integatr starts moving down. 90, 80, 70, 20. When this happens Blm adjust as expected, 128, 125, ending at 120 where it stays. If I drive at highway speeds the computer is able to adjust well enough to keep from setting a code. 02 works, ranging from .2 to .9. The car still wants to run rich but the computer is able to keep up. As soon as I drive in the city, 02 goes up, .9 and generally stays there. BLM at 120. Integratr 20 or so. 10 minutes of these parameters and the computer gives up and goes into Open Loop, integratr goes back to 128 and stays there, BLM seems to stay at 120.. With hard driving it will go back to closed. Fuel pressure running is 38. I blocked off the cold start injector today. Seemed to help slow the decay, but same overall result, running too rich. Should the BLM go lower than 120? I've run out of ideas. The car is running rich but I don't know why. Thoughts? Thanks, JM Patrick AUG 23, 11:28 PM Does your fuel pressure hold when the engine is turned off? If it doesn't, it's possible your fuel pressure regulator and/or an injector are leaking. Are there any cracks/leaks in your exhaust system ahead of the O2 sensor? That would cause a rich mixture as well. mountainman AUG 23, 11:35 PM Fuel pressure drops about 4 lbs in 10 minutes. I wouldn't think that would be enough of a leak to run this rich. Not really sure where the PSI are going. There may be an exhaust leak. I occasionally think I hear what would sound like a header leak. But not often. Worth further checking. j mountainman AUG 24, 03:54 PM Well I found the exhaust leak. Almost wish I hadn't looked. Firewall side exhaust manifold, #2 cyl. Looks impossible to get to without removing the engine. Air conditioner pump in the way. I can't even see the bolts. If it can be done another way, please let me know. Thanks. j mountainman AUG 24, 03:55 PM Patrick AUG 24, 07:06 PM quote Originally posted by mountainman: Firewall side exhaust manifold, #2 cyl. Looks impossible to get to without removing the engine. Air conditioner pump in the way. Exactly the situation I faced with my '86 GT, complete with the A/C pump in the way. Turned out I had two exhaust manifold bolts broken off in the head. It was the worst freakin' repair job I've ever done on a vehicle in the almost 50 years I've owned a car. I removed the two rear cradle bolts and tilted the cradle down to open up some room to drill out the broken bolts. If I had to do it all over again, I think I'd pull the head instead. mountainman AUG 25, 12:46 AM I was afraid of that. Been thinking of putting in a new clutch. I guess I'll fix this problem then. I'm expecting broken bolts as well. It runs ok, most of the time, I can live with it for now. Thanks Patrick. j Patrick AUG 25, 01:59 AM quote Originally posted by mountainman: Been thinking of putting in a new clutch. I guess I'll fix this problem then. I'm expecting broken bolts as well. If, and that's a big IF there aren't any front exhaust manifold bolts broken off, then dealing with the exhaust leak can be done "easy" enough with the engine in the bay... but more than likely there will be broken bolts... and yeah, dealing with it while the cradle is dropped for a clutch job makes good sense.