85 suddenly running bad
Thread Starter
Instructor
Joined: Oct 2009
Posts: 202
Likes: 9
From: Tucson
85 suddenly running bad
On the way home from work today, my 85 auto started to run sluggish, then very bad. It is mostly stock with these mods: BBK TB, cut lid, MAF screen cut, 8 BTDC. This is what it was doing:
I didn't have a chance, but tomorrow i'm going to check the usual suspects: TPS setting, visual check of MAF, check for vacuum leaks, timing check, etc.
Is there anything apparent I should check given these symptoms? Any help is definitely appreciated.
- When I nail the throttle, it bogs bad, and sometimes doesn't downshift.
- It sounds like its detonating bad, and won't rev very high
- When I put it 1st gear and nail it, it bogs, detonates, and then upshifts at about 2900. Normally it would upshift at around 5100.
- There is NO error code
I didn't have a chance, but tomorrow i'm going to check the usual suspects: TPS setting, visual check of MAF, check for vacuum leaks, timing check, etc.
Is there anything apparent I should check given these symptoms? Any help is definitely appreciated.
Thread Starter
Instructor
Joined: Oct 2009
Posts: 202
Likes: 9
From: Tucson
OK, still running bad. This is what I checked so far:
Fuel pressure good
TPS set right
Timing correct
Checked MAF according to FSM
Disconnected MAF, car ran worse
visual check for vacuum leaks
Still no error code. The car will run OK at part throttle. Will bog and detonate at WOT. Could the EGR have something to do with it? Could the MAF be bad and not through an error code? I am completely lost at this point.
Fuel pressure good
TPS set right
Timing correct
Checked MAF according to FSM
Disconnected MAF, car ran worse
visual check for vacuum leaks
Still no error code. The car will run OK at part throttle. Will bog and detonate at WOT. Could the EGR have something to do with it? Could the MAF be bad and not through an error code? I am completely lost at this point.
Burning Brakes
Joined: Aug 2010
Posts: 833
Likes: 1
See what the fuel pressure is with the engine under load. I found that when I had fuel problems with my car, they didn't show up until I tried to accelerate. There shouldn't be anything wrong with the MAF if it ran worse when you unplugged it.
Thread Starter
Instructor
Joined: Oct 2009
Posts: 202
Likes: 9
From: Tucson
I attached a fuel pressure gauge to the rail, and then stuck it out of the hood. Under acceleration it was still doing 40 -42. Its definitely getting fuel.
The weird part is that it runs fine part-throttle. Its only at WOT that the problem occurs.
Could it be caused by the tranny not shifting correctly? That is, if the tranny doesn't downshift when I go WOT? It is kinda strange that when I put it in first gear the tranny shifts automatically very early, like 2900, vs. 5100 when it was running right.
The weird part is that it runs fine part-throttle. Its only at WOT that the problem occurs.
Could it be caused by the tranny not shifting correctly? That is, if the tranny doesn't downshift when I go WOT? It is kinda strange that when I put it in first gear the tranny shifts automatically very early, like 2900, vs. 5100 when it was running right.
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