I'm getting tired of battling this, so I'm turning it over to you all.


Car in signature has the following problem.


Cruising along before 3800 RPM - AFR's around 14.2-14.6. A little leaner than I would like, but it's low RPM's and all in vacuum so whatever. If I open up the secondary throttle plates, the car will start to build a little boost. The AFR's will dive down to the low 13's, pause for a second, then start to come back up and wind up where they were at - 14's. No matter if I floor it or just build 1-2 pounds, this always happens. It will start to buck around and surge if I don't back out immediately - obviously it doesn't like to see those AFR's either.


Above 3800 when the secondaries come on, it runs pig rich just like it should and has tons of power.

Also, at idle, it runs at about 10.5-10.9 AFR. That's obviously wayyyyy too rich, but if I back out the variable resistor or play with the screw in the AFM to lean it out, it will start idling rough and wanting to shut off.



My TPS is 100% dead on.

One theory I have is that I have blown my FPR vacuum line off the nipple on the inside of the lower intake manifold. That is quite possible because when I put it on, it was a little loose. Does anyone else have any ideas on what could be wrong? Primary injectors going down the crapper?

 

What are you controlling the fuel with? The bucking from it running way lean is probly not doing your motor good either so you might try to avoid it.

 

dunno. but it wouldn't hurt to replace that vacuum line.

 

Stock ECU.

 

Well thats your problem. You need to get at least a Apexi SAFC or something to that nature.

 

Are you running a boost controller?

Im asking because if you have a mbc, the boost response is quicker. So your going to get more air in the begining during spoolup

 

Yes, there is a boost controller on there.

I took the UIM pff today to check that vacuum line and everything is good under there. I put it together and took it for a drive and it seemed fine as far as AFR's go. The only time that it would lean out was when I floored it at 2-3,000 RPM's. I will chalk that up to me not having a restrictor pill in the MAP reference line. But it seemed to richen up just fine when I gradually rolled it into boost.

SAFC is top on my list of "Things to buy when the money shows up."

 

You mean rich, right? 14.2-14.6 is too rich for light load. 15:1 is more like it.

How are you measuring this? Do you have a wideband installed? Your signature indicated a narrowband A/F meter. If this is the case, then reading it is a bit tricky.

How much boost are you seeing when the car begins to buck? You may need upgraded primaries.

The car should never run pig rich. On the stock turbo in boost you should be seeing low 12s/high 11s.

That is insanely rich. Again, how are you reading this? At 10:1 the car will be blowing black smoke from the tailpipe.

If the FPR was disconnected the car would be very rich at idle, but very lean under boost. You would also have a noticable vacuum leak.

 

It is a narrowband, but it does a good job of "letting me know."

It begins to buck under 3-4 pounds. It's not so much the boost, as it is how far the throttle is open. If I open the secondaries anymore than a hair it will lean out and start to buck. If they are open a hair, it dives from mid 14's down into the 13's, but if I hold the throttle steady, it will start to shoot back up after in boost for maybe 5 seconds. If I open the secondaries anymore than a tad, it will go lean as soon as the boost starts to build, shoots straight up to 15's and begins to buck.

It does blow a little smoke at idle, and floods easily if I shut it off and try to restart.... runs very rich at idle.

I'm beginning to think that my primaries are in need of replacement (They do have 110,xxx miles and grime all over them....).

 

Drove it again tonight, and on the highway in 5th, as soon as it went into positive pressure, AFR's shot straight up.

TPS is in spec, 1Kohm at throttle closed and 4.7Kohm at WOT.

Is there anyway to check my AFM and MAP sensors? I guess I can look in the FSM. Other than one of those sensors sending bad readings, I guess I will go ahead and buy 2 720's and bump my 690's down to the primaries. Can't hurt anything even if that doesn't turn out to be the problem.

 

Dude you need to get some way to control the FUEL. Also get a wideband. Do those two things before anything. With a Apexi it would be pretty easy to richen it up where you need but running lean like that has more than likely Detonated a few times which is BAD.

 

I have not been driving it in boost, because I know it is detonating when it does. I lost an engine to detonation 2 months ago, not trying to do it again.


I should not need anything to control fuel. I can't even get it to hold 2 pounds without leaning out. Something isn't telling the ECU that it needs to wake up and dump the fuel. I just tested my AFM as per the FSM and it's all good to go. I will check the MAP tomorrow. Those are the only 2 sensors I can think of that would make the car act like this.

 

Maybe you need to rewire the fuel pump? If its stuck in low voltage mode or whatever, I guess that would mess it up.

Oh wait, you have an 87, I forget if they have the switchy pump too.

 

You can't accurately measure idle mixtures with a narrowband.

Cleaning the injectors is always a good thing, but in your case I don't think it's the problem.

Seeing 13s under 2 PSI is not an issue, but under higher boost it is especially if it leans out further.

In a case like this I'd recommend that you find or borrow a wideband to make sure are chasing the correct problem.

Check fuel pressure as well. Is the regulator connected to a vaccuum port?

 

Today I added a ground to the MAP ground (It's an 87 car but was made in 12/86), and resoldered my ECU grounds to the floorpan (they were pretty haggard, I tried soldering them with a ghetto soldering gun last time.....). I set the idle tonight and drove it just up the street and back, but as soon as it went into boost it was dumping in fuel like it should be.

I don't want to say whether it's fixed or not, but I will test it some more tomorrow. I'm also going to run a bottle of Seafoam through it and a bottle of Techron in the gas next fill up.

 

Putting stuff in the fuel tank is not going to solve the problem. The grounds may have helped but I'd be surprised if they did.

 

Why not idle the engine, then reach around under the back of the engine and pull the FPR line off. It either has or does not have vacuum. No vacuum? Fix it. I'd have done that earlier when you were *wondering* about it. Takes five minutes.

 

exactly. vac leak = more air = lean out.

 

There's vacuum at the FPR, I checked hat last weekend. I will drive it some tonight, but it seemed to drive much smoother last night and it definitely idles a lot smoother.

 

Hate to break your heart, but either the MAP ground or the re-doing of my ECU grounds did the trick. AFR's are consistently 11's/low 12's from 1 pound all the way to 6 pounds, as well as smoother-running in general.

Seafoam'd it today. Seemed to help it out a little, although I'm sure it killed my plugs.

 

Either way, I'm glad it worked!

 

I am too.... now to get some new plugs, a motor mount, and port my wastegate. Always work to do........

 

You can't accuretly read your AFRs with a narrowband sensor. You need a wideband sensor for that, as stated by Aaron Cake

 

Well..... the car is back to it's old ways. It ran perfect last night and this morning, but this afternoon coming home it started wanting to lean out again.

Sometimes it will run fine, other times it will just lean out.

I'm checking the fuel pump resistor relay tomorrow..... but I'm really getting sick of it.