Check and see if the combs are in the maf, do a boost leak test, and BIS.

1. Do the combs pop out spontaneously?

2. I should do a boost leak because I haven't in awhile, but wouldn't a boost leak cause a rich condition, not lean?

3. BIS is the screw that you can adjust idle with right? Are you suggesting it can leak boost or that I need to adjust it?

You should put the right heat plugs in, 6es. The 7es plugs are colder.

Boost leaks cause lean at idle and rich under boost.

Biss screw can leak, along with the shaft seals in the throttle body.

I would up your fuel pressure to where it should be. 43psi at the AFPR with the vac hose off.

When my car is at idle I set it at 14.8 with my safc and then if I wait my car all of a sudden jumps straight to 17 then I goes back to normal then goes all over the place.. what can this be

Do you have a wideband? Are your o2 sensors working properly? Any boost or exhaust leaks?

NoHndlbrsRqrd said:

You should put the right heat plugs in, 6es. The 7es plugs are colder.

Boost leaks cause lean at idle and rich under boost.

Biss screw can leak, along with the shaft seals in the throttle body.

I would up your fuel pressure to where it should be. 43psi at the AFPR with the vac hose off.

Click to expand...

Thanks for your help, I'm already running fresh BPR7ES gapped at .028-.030

Mark4g63t said:

Do you have a wideband? Are your o2 sensors working properly? Any boost or exhaust leaks?

Click to expand...

I do have a wideband. The narrow seems okay, due to your suggestion of the o2 sensor I will have my wideband emulate my shortband today via my tuning kit to rule out o2 sensor issue.

Detailed symptoms:
Car idles pretty normal, drives pretty normal, fuel is normal at idle.
When I get on it at part throttle and spool turbo, car feels normal
When I go WOT my car it has a SMOOTH loss of power, its not jerky or stumbling, engine and turbo sounds normal just loses power.

So this is what I have done:
1. Cleaned my air filter
2. changed my plugs BPR7ES with proper gap (.028-.030)
3. Did a compression test, this was NORMAL
4. Fixed boost leaks (had a pretty bad one)
5. Increased my fuel through ECUPLUS to see what would happen, I was able to get it pig rich with no change in symptoms (roughly +40-50% to obtain this)
6. Checked my turbo, seems good, no shaft play, spins freely.
7. Checked fuel pressure at the filter at IDLE it is NORMAL, can't check it at WOT because I just have an under hood guage
8. Brought my car up to the local Oreilly auto parts store to have the alternator and battery checked, battery was normal, alternator voltage was normal, ALTERNATOR AMPERAGE WAS VERY LOW (<30 AMPS, the machine doesn't read below 30)

Here is what I'm thinking: There is low fuel at WOT, this makes me think I'm getting not enough fuel, (I checked to make sure no unmetered air is getting in). It is probably not injectors because my plugs are white across the board and car runs normally at idle. Its probably not spark related because of the SMOOTH loss of power, I read on the forums from a knowledgeable guy that ignition problems usually caused stuttering and sudden sporadic loss of power. The car is not smoking or anything else unusual.

So I have these possibilities in my head:
- Could by caused by obstructed fuel filter that is limiting flow at WOT but flows enough for idle
- Could be caused by fuel pump going back that is limiting flow at WOT but flows enough for idle
- Could be caused by FPR or vaccum hose, however, I doubt it because it is reading normal with and without vacuum line attached
- Could be caused by a BAD ALTERNATOR that is unable to pump out enough amperage to the pump to maintain pressure at WOT


Any Input at all would be greatly appreciated. As you can see I'm trying very hard to figure this out. I'm going to swap alternators here in a bit I will post after its completed.

Voltage drops at higher rpms will cause the lean conditions. It affects fuel pump, ignition, injectors, sensors...all of it. Can you log your car? That would tell you where the voltage is at.

Alternator turns off at WOT.

So it came to my attention that the alternator was tested idling and the guy at the shop said it was below 30 amps so needed to be replaced. I looked into my car records and is diagnosis was nonsensical because that would be normal at idle according to my alternators papers. I should have caught that at the shop. So I returned it.

I changed my fuel filter instead. Fuel pressure is now 58psi or so with fpr vacuum removed and 50 connected at idle, it previously was 43 psi without vacuum and 38 on vacuum. Car runs the same or maybe slightly better. Still lean, still not right.

What is the meaning of that fuel pressure change? I'm confused.

Forgot to mention compression test showed 200 psi on all four cylinders. I know it's a bit high but it was like that when it was running well also

Denji said:

So it came to my attention that the alternator was tested idling and the guy at the shop said it was below 30 amps so needed to be replaced. I looked into my car records and is diagnosis was nonsensical because that would be normal at idle according to my alternators papers. I should have caught that at the shop. So I returned it.

I changed my fuel filter instead. Fuel pressure is now 58psi or so with fpr vacuum removed and 50 connected at idle, it previously was 43 psi without vacuum and 38 on vacuum. Car runs the same or maybe slightly better. Still lean, still not right.

What is the meaning of that fuel pressure change? I'm confused.

Forgot to mention compression test showed 200 psi on all four cylinders. I know it's a bit high but it was like that when it was running well also

Click to expand...

You don't test compression running. And you should reset your fuel pressure. I've done that before, set it to what I thought was 43, got an issue, rechecked and it was 50+.

MJcanada said:

You don't test compression running. And you should reset your fuel pressure. I've done that before, set it to what I thought was 43, got an issue, rechecked and it was 50+.

Click to expand...

I meant the compression is the same as when it ran well, it was of course checked with the vehicle off and at operating temperature.

I can't reset it because it's the stock unit. I do have a spare so I could replace it or order an adjustable one.

Thanks for the responses.

Swapped fuel pump, A/F ratio went down to 10.2 during WOT. Seems like it solved the issue. The filter on the back of the pump was very, very dirty so it could have been related as well.

I'm bringing this back from the dead to give an update. This problem returned later and the car mostly sat for several years and I didn't mess with it. The problem seems to be related to a boost leak I missed at the throttle body. Becuase the car was running poorly I turned down the boost. This fouled my plugs very quicky as I should have been running BPR6ES.

So I put in rebuilt throttle body, went to BPR6ES gapped at .30 and its running well at stock wastegate.

Now I'm going to up boost and retune.

Shout out to
NoHndlbrsRqrd
For calling the wrong plugs for my boost level and throttle body boost leaks.

...since you bumped this... ECMLink is a great diagnostic tool, post your log while you're describing your symptoms too.

I am having the same problem as you and I do have a leak at the tb seals. I didn't think that a relatively small leak like that could cause such a big power loss. Mine happened suddenly too and I didn't think that would happen either. If anything changes would you please update? Thanks!

Also, where did you get the rebuilt tb from?

bibdrums said:

Also, where did you get the rebuilt tb from?

Click to expand...

throttlebodys.com is where I got my rebuilt one from

Hopping in to clear up some of the bullsh*t.
@gofer hit it on the money with the recommendation for Link. Being able to look at fuel trims and whatnot makes diagnosis a snap.

Stock spark plug for ‘95-‘96 is a BPR6EKN per FSM, but we ALL refer the BPR6ES. Gapped 0.028-0.030 or 0.031 (depending where you look)
I personally recommend the BPR6EIX’s gapped 0.028-0.030
Note: common recommendation is to start stepping down as power levels increase.
I believe I ran the BPR or BKR6EIX when I first got my car and did maintenance. I now run a BKR7EIX plug with an EVO III 16G and supporting mods.

An oxygen sensor is an oxygen sensor —> it only senses oxygen. If you’re fouling plugs causing a misfire —> You’re sending a whole lotta oxygen (albeit with hydrocarbons —> but remember we’re only pulling o2 content) that hasn’t been used straight down the pipe. You now have a lean condition.
I would readily say a boost leak causes a rich condition. HOWEVER, I know that if I’m misfiring —> I can get a lean reading on o2.
So back to strictly boost leak, I can theorize that IF it is bad enough to cause a misfire, then a boost leak CAN cause a lean condition.

Onto the ampere thing. Some f***ing people annoy me. Based on that info you gave, that wasn’t a proper test. If you want amps on the entire system (including battery) clamp battery negative. If you want what’s being demanded from the alternator at any given time —> clamp power off alt.
If you want to test alternator —> you can supply ground to sense / signal so alternator can energize it’s field and put out full power. At that point, you can clamp alt feed and take a reading.
Sometimes it’s easier to let the Autozone machine do it.

Depending on what year DSM you have. Your base fuel pressure may be different. Always revert to FSM for such good information...
‘95-‘96 is 42.0-44.8psi per fsm (I like 43.5) @ 750rpms (+/-100) w/ vacuum disconnected
‘95-‘96 is ~33.4psi per fsm @ 750rpms (+/-100) w/ vacuum connected


Between the 3-4 DSM’s I’ve messed with between myself and my friend. A common boost leak is in fact the throttle body. Check / spray both gaskets, check / spray both sides for the shaft seals, check / spray BISS screw for o-ring sealing. Basically you might as well spray the whole house. Lol. I literally had to replace it all on my car. Again, NOTORIOUS area for leaks.

So many different compression testers and so many people actually do the test not perfect (I’m not saying incorrectly).
‘95-‘96 FSM standard value is 178psi w/ max pressure difference @ 14psi between highest and lowest readings.
I always take this a step further —> 14 / 178 = ~8%.
The recommended norm anyway is you want to see <10-15% fluctuation across all cylinders. I always encourage people to use common sense and just keep it simple with this test.
An example —> you have three cylinders at 150 and one at 87, then you better start looking at what’s up with the one reading 87...