:driving: Turbo Boost Gauge readings

[nvno1]

Originally Posted by NoDOHC

If the idle is above 750 and the engine is warm, the BAC should be shut. If you unplugged it and the pulsation didn't go away, I doubt that it is the issue. The stock ECU has a 'hole' in the timing map to make the engine idle down while getting excessive air and fuel (5 degrees ATDC). If I program a similar hole into my Haltech, it will do the same oscillations if I set the idle too high. Seriously, try adjusting the idle down to 750 with the check jumper connected and then see what it idles like.

This still doesn't explain why the engine is running at such low vacuum. You said that it revs very quickly from idle if you floor it?

Are you sure that the timing is correct?

By press the TPS in all the way, you mean floor the gas, right? Pressing in the TPS without moving the pedal shouldn't make the engine rev to the redline.

This is going freak you guys out..

the car starts after a few cranks(no bac connected) ..however if i play with the pedal it starts up..stutters a little then she picks up...i have to play with the gas at little to keep her running. after about two mins of that she will run with no pedaling of the gas pedal. she is still looping.

when under the hood and i press in the TPS plunger, not by way of the pedal, the rpms start climbing.......crazy i know.. the timing was set by way of the FSM...aligning the second notch(if facing the car,second notch to the right) on the main pulley to the needle on the front cover(gslse) and the cas has been removed and placed back with the little circle mark on the gear wheel with the pointer on the shaft on the cas.

[NoDOHC]

I hate to say it again, but this sounds like a vacuum leak (it may be a mal-adjusted bypass screw in the AFM - if S5 Turbos have it).

If the engine revs when the TPS is pressed, it must be getting air from somewhere. It is probably running really lean and the Idle adjust screw is turned out so far to keep it running that it really is idling with that poor of vacuum.

Are you pushing the part-range or full range TPS? (I think that the part-range TPS is pressed when the throttle is shut, so I am guessing that you are pressing the full range TPS).

My theory is that you are pushing the full-range TPS in, which is causing throttle enrichment, which is allowing your woefully under-fueled engine to rev up. This also explains your idle vacuum issue (a large vacuum leak has no air going through the AFM when there is significant vacuum because it all comes in the leak).

Places to check:
Input to BAC Valve
Injector Pintle cap seals
emissions removal plates (if you have them)
cruise control (if you have it)
Vacuum Booster for brakes.

Let me see if I can describe what the engine is doing.

If you try to crank it without pushing the gas pedal, it will not start.
If you rapidly pump the gas pedal while cranking, it will try occaisionally (almost always as the gas is being pressed down) and will eventually start.
Once running, it revs to about 2,000 rpm, at which point it is misfiring so bad that it dies.
On the way down, the engine catches about 800 rpm, it fires several times in a row which causes it to rev to 2,000 rpm again.

If this is what it is doing (which I think you have already described) then it is running too lean to fire as it revs up. This is almost a dead giveaway for a vacuum leak. The only other possibility is that the FPR is referenced to a ported vacuum source (which shouldn't make this drastic of a change).

Edit: Things to try.
Press the Full Range TPS in and hold it in with the BAC unplugged. If my theory is right, it will rev for a little while, reach 3,000 to 4,000 rpm and start to stutter and eventually return to the loping idle.
Take off every vacuum line except the one to the MAP sensor and the FPR and plug the holes.
Make sure that you have the correct AFM for the car.
Get more carb cleaner or a smoke machine
Watch your fuel pressure (I doubt this is it).

[TitaniumTT]

you have an engine that produces 85 psi of compression. That is below what Mazda considers the minimum for a running engine to produce. It's no wonder that your engine hunts, idles poorly, and pulls lower than average vacuum. It's becuase the engine is old and tired or improperly rebuilt. My ported RE makes 120-125psi of comp on all 6 faces and pulls ~15" vac at a 750rpm idle and it hunts a little. I bumped the idle to 1000 rpms and she'll pull 19" of vac all day and not hunt around much at all.

I think you're chasing a problem that doesn't exist. How did you run your comp test?

By the way, I noticed that you said you're adjusting things per the gsl-se FSM. That is WRONG! You need to adjust things per the FSM that the engine belongs to. If the motor came from a 86-86 TII car, that's the FSM that you need to be looking at for adjustment.

[Max777]

I had a very simmilar problem with my 91 N/A.... that motor tested out 82psi compression. I never did figure out what the problem was before parting out the car, but I did alot of the same stuff that you did, and it just never liked to stay running.

One thing to check: Check the adjustment for the thermowax pellet on the throttle body, mine was out of adjustment and ran a lot better after I readjusted it to FSM spec.

[RETed]

Originally Posted by nvno1

front cover(gslse)

Ar you using the GSL-SE CAS too?
If not, can you verify that the GSL-SE and FC front cover pin locations are identical?
I don't like the idea that you're mixing and matching parts like this...


-Ted

[nvno1]

Originally Posted by Rx-7fetish

Sounds like tps to me, have you checked it besides poking it with your finger, mainly the test lights or volt meter?

sorry for the delay in responding...the tps has been checked with lights and multimeters..it appears to be good.

Sounds like your afm is going bad or there is an intake leak after it. I had the same symptoms on both my 10th ann and an 87 gxl, the 10th ann had an intake leak between the afm and the turbo, and the afm was going bad on the gxl.

I just got my block off plates, new waterpump housing and upper intake gaskets. when i take her apart i will change the clamps with some clamps i can tighten down...thanks for the input..if all else fails i will change the afm and the tps even though both tested fine.

[nvno1]

Originally Posted by NoDOHC

I hate to say it again, but this sounds like a vacuum leak (it may be a mal-adjusted bypass screw in the AFM - if S5 Turbos have it).

If the engine revs when the TPS is pressed, it must be getting air from somewhere. It is probably running really lean and the Idle adjust screw is turned out so far to keep it running that it really is idling with that poor of vacuum.

Are you pushing the part-range or full range TPS? (I think that the part-range TPS is pressed when the throttle is shut, so I am guessing that you are pressing the full range TPS).

My theory is that you are pushing the full-range TPS in, which is causing throttle enrichment, which is allowing your woefully under-fueled engine to rev up. This also explains your idle vacuum issue (a large vacuum leak has no air going through the AFM when there is significant vacuum because it all comes in the leak).

Places to check:
Input to BAC Valve
Injector Pintle cap seals
emissions removal plates (if you have them)
cruise control (if you have it)
Vacuum Booster for brakes.

Let me see if I can describe what the engine is doing.

If you try to crank it without pushing the gas pedal, it will not start.
If you rapidly pump the gas pedal while cranking, it will try occaisionally (almost always as the gas is being pressed down) and will eventually start.
Once running, it revs to about 2,000 rpm, at which point it is misfiring so bad that it dies.
On the way down, the engine catches about 800 rpm, it fires several times in a row which causes it to rev to 2,000 rpm again.

If this is what it is doing (which I think you have already described) then it is running too lean to fire as it revs up. This is almost a dead giveaway for a vacuum leak. The only other possibility is that the FPR is referenced to a ported vacuum source (which shouldn't make this drastic of a change).

Edit: Things to try.
Press the Full Range TPS in and hold it in with the BAC unplugged. If my theory is right, it will rev for a little while, reach 3,000 to 4,000 rpm and start to stutter and eventually return to the loping idle.
Take off every vacuum line except the one to the MAP sensor and the FPR and plug the holes.
Make sure that you have the correct AFM for the car.
Get more carb cleaner or a smoke machine
Watch your fuel pressure (I doubt this is it).

Hey NoDOHC, sorry for the delay...dont have access to a pc right now..in my last post i stated that i have a block off kit and will change my gaskets while i have the car apart i willdouble check the hoses and the AFM...I am hoping that it is a vac leak.


the starting thing is mainly just holding the pedal down a little bit. and i only see one TPS i have a 87TII S4

[nvno1]

Originally Posted by TitaniumTT

you have an engine that produces 85 psi of compression. That is below what Mazda considers the minimum for a running engine to produce. It's no wonder that your engine hunts, idles poorly, and pulls lower than average vacuum. It's becuase the engine is old and tired or improperly rebuilt. My ported RE makes 120-125psi of comp on all 6 faces and pulls ~15" vac at a 750rpm idle and it hunts a little. I bumped the idle to 1000 rpms and she'll pull 19" of vac all day and not hunt around much at all.

I think you're chasing a problem that doesn't exist. How did you run your comp test?

By the way, I noticed that you said you're adjusting things per the gsl-se FSM. That is WRONG! You need to adjust things per the FSM that the engine belongs to. If the motor came from a 86-86 TII car, that's the FSM that you need to be looking at for adjustment.

must be nice to have a freshly built motor...i miss those days (except the break in part)..the way i tested the compression was with a reg compression tester with the valve taken out and cold. i got 3even pulses. A friend of mines who builds motors told me the compression is okay , not great but okay. you noticed i was adjusting things per GSLSE FSM? where did to get that? i have the 86-88 FSM on hand.

[nvno1]

Originally Posted by RETed

Ar you using the GSL-SE CAS too?
If not, can you verify that the GSL-SE and FC front cover pin locations are identical?
I don't like the idea that you're mixing and matching parts like this...


-Ted

Hey Ted,

i had no choice but to use the GSLSE front cover it a TII swap in a GSLSE. and the GSLSE uses a dizzy. im using the cas that came with the 87 motor. the pin looks to be in the same location.