I've been posting this problem under "Sluggish Formula 350" thread in the general tech boards, but I thought I'd try here for help as well...

To sum up... It's an 89 L98, no mods at all. I've been getting really poor gas mileage (10 mpg city, 20 mpg highway) and the car in general seems rather sluggish (my only basis for comparison is an 82 305 TA I used to own).

I've replace CTS, O2, plugs, wires, cap, rotor, fuel filter, air filter, etc. TCC seems to be locking up.

This weekend was my first try at using Craig Moates software. Just checking at idle. All the numbers seemed to with in spec (according to the service manual)... but the BLM was 146-149.

Can anyone help out? (Even pointing me to the page in the service manual that referred to BLM when troubleshooting would be great.)

I'm at the point now where I don't want to throw parts at it and I don't want to check everything and hope I stumble onto what isn't working.

Thanks all.

 

Get a fuel pressure gauge and check the actual pressure at the fuel rail with the vacuum line to the regulator removed and capped. The high BLM shows it's adding fuel, maybe compensating for low system pressure.

Aside from that, I'd pull all 8 spark plugs again and read them for indications of abnormal combustion. If you have one or more injector(s) underflowing the plug(s) will show it clearly.

Keep us posted.

-Kevin

 

Well.. checked the fuel pressure. It seems okay. I followed the steps for checking it in that are in the service manual. 46ish when the pump first comes on... drops immediately to 41ish when it shuts off after 2 seconds. At idle, it held steady at 36ish.

(I can't remember the numbers, but I do know they were within the specs specified in the service manual.)

When the pump shut off, you could notice the pressure bleeding away, but it was very slowly. Maybe 1psi a minute or so? How fast/slow should it bleed off?

Also, from the service manual... it says if BLMs go over 138 to check the conditions that also cause a code 44 (or 45... the code for a lean O2 sensor reading). One of the checks was to disconnect the MAF sensor. If the lean condition goes away, replace the sensor. (The service manual did not elaborate any more than just that...)

When I did this, my BLMs dropped to 118ish (at idle). That to me seems like the lean condition is gone. Is that right? If so, are there any other checks I can do with the MAF to check if it's bad? It's rather pricy, so I don't want to replace it if I don't have to. At idle, and hooked up, it reads 6g/s which is also within the specs mentioned in the service manual.

Also, I didn't pull the plugs yet. I must admit I'm procrastinating on that one. Not exactly a fun task. But when I do, what would indicate an underflowing injector? Would I only need to pull the left side since that's the only side the O2 sensor would be reading? (Of course, if that turned out to be the problem I'd check the other side, but right now I'm more interested in finding the cause of the problem.)

Sorry for the long post. And thanks for any thoughts/help/ideas you can give me.

-Dave

 

Anyone?

 

I feel like I am in the same boat as you, or at least the same lake. I have the same engine as you and alot of the same symptoms you describe; bad gas milage, performance and throttle response not to mention BLM's that are higher than they should be. I have replaced all of the components you mentioned and a few others; pcv valve and the ignition module(it completly failed on me, which might or might not be related?). I do however have a few modifications(check my sig) done to my car. You question the performance of your injectors and your MAF, which after the diagnosing I have done so far is where I am at. I bit the bullit and sent my injectors out last week to cruzin performance to have them tested, cleaned and then re-tested. To my disappointment, they told me that even before they were cleaned they flowed within 3% of each other; factory tolerance being between 7-10%. So much for blaming it on my injectors , they also told me that it is common for 350 tpi injectors to be real consistant with each other even when dirty. So now I am sitting here looking at the most expensive sensor on my engine and scratching my head ?? What service manual are you refering to and in what section does it give the diagnostics for the MAF that you mention? You also spoke of fuel pressure. I have a gauge and mine seems to be good at idle, but I have yet to check it under load. I have heard this is a sign of a bad pump and can lead to lousy performance. Did you check yours under load? I figure a nice power-brake burn out with some one peeking under the hood will be an effective and fun way to check this. Sorry about the long post, but I feel putting our heads together on this could save us both some time.

 

I would not believe that it would be the MAF. Usually they just go bad at once, not lose metering ability. Did you check the fuel pressure just at idle? You might try driving with the test gauge taped to the windshield to see if the pressure fluctuates while driving down the road. Also you might need to clean the injectors. The BLMs as you probably already know should be 128 in a perfect world.

 

It's the factory service manual that I was using. (Picked it up from http://www.kenmcgeeautobooks.com/ for $90 Canadian.) I'll see if I can't scan the pages I've been looking at for you. I actually find it a pain in the *** to find what I'm looking for in it.

I didn't check the fuel pressure under load. I just followed the flow chart described in the service manual for diagnosing the fuel system, and it rather quickly told me to look elsewhere for the problem.

As I mentioned, the only indication I have that my MAF is bad is that comment in the service manual about unhooking it and replacing it if the lean condition went away. Which it did, but it went really rich (BLMs went to 118ish).

 

You are right about the service manual saying that if disconnecting the MAF would solve the lean condition it should be replace. I think this is a very broad statement. If your readings were on the money and you removed your MAF you would go rich anyway (limp home mode) since the computer would try and protect the engine as a failsafe. In the Lack of Power, Slugish, or Spongy page it suggests checking the EGR for being open or partly open at all times and exhaust restrictions (Cat converter).

 

So far I've been focusing more on getting the gas mileage up to where it should be (15ish city/25ish highway right?). That and the high BLM count are the only measurable aspects of it. I'm surrounded by people who keep saying the engine has lots of power. These are also the people who seem amazed when I say "5.7L" though.

 

Well, it can't hurt to stay on top of the little things. You said the plugs / wires / etc are fresh. Have you since pulled the plugs to see what they look like. With that broad a range in mpg i'm assuming you do a good amount of stop/go or cold engine driving. Thats an easy recipe for fouling plugs. Happens to my car all the time in the winter with my short drive to work. I do some long highway driving too though and that cleans em right up.

Now, couple on to that...have you verified that your timing is set properly. If you haven't touched that in a while, it is defintely a mandatory stop. Timing retarded just a few degrees from stock will definitely cause the engine to slump.

With the high BLMs, your obviously adding a bunch of fuel and the computer thinks the O2 is lean. A vacuum leak, especially localized on the pass. side runner (drivers side exhaust / O2 sensor) would cause it to see lean, while the other half of the engine went dog rich.

Pull your plugs (at least a few), say after driving to work a few days and after a long highway trip. That'll give you some idea of what is happening in the different cylinders. At this point, that'll be 20x more than you know right now...

 

I had the timing set when I did the plugs and wires... but I'll get that double checked this weekend. (Man I gotta get a timing light of my own....)

So I guess I'm in for some banged up knuckles this weekend.
I'll bite the bullet and pull the plugs. Maybe it'll go easier this time. LOL

Thanks for the help guys... I'll let you know what I find out.

Oh... any one have any tips on finding looking for a vacuum leak? Do I need a vaccum gauge? I was under the impression that a vacuum leak would cause a rough idle. Mine seems to idle fine, so if there is a leak, I take it it would be rather small and hard to find?

 

A vacuum leak won't necessarily cause a rough idle. Thats more a hold over from old carb tips. It could just cauyse the one side of the engine to run perpetually rich by leaning out the other side. This wouldn't necessarily make it idle that bad. You never know. This isn't a cookie cutter problem. You have to eliminate all possibility's. It's not hard to spray some carb cleaner to check for leaks, or simply check torque on the runner bolts / base even.

 

Just so I don't go and do something stupid.... when I'm checking for a leak should I just be spraying carb cleaner around the plenum/runner gaskets or the hoses as well? I would have thought carb cleaner would be bad for the plastic/rubber.

And how do I know if I've found a leak? Hook the scan tool up while I spray, and look for the BLMs to go down? (The carb cleaner plugs the leak correct?)

 

No, it's easier than that. I did it to my car and found nothing, that's good I guess? It didn't seem to harm anything, and I think I sprayed it just about everywhere. You want to listen to your cars engine speed, I guess you could use your scanner for this if you didn't want to just do it by ear. If you do spray some of this flamable fluid on a vacuum leak, theoretically your engines speed should increase. It's a really quick and easy test to perform. Another thing I did that you might want to consider while your squirting things under your hood is an arcing test. Have you doen this yet? It's another easy one. With your car idleing you just mist all of the spark plug and coil wires with water and watch for any blue arcs (aka shorts), obviously this is easier done at night.

Good Luck lava

 

Ahhhhh... got ya.

Thanks everyone. I'll see what I can find out over this weekend.

 

Okay, so here's where I'm at after the last couple of weekends.

Found a vacuum leak and replaced the hose. That brought the BLMs down from 144ish to 135ish. Went for a highway drive (100 miles) before pulling the plugs. Fixing the vacuum leak did nothing for gas mileage... I still got 18mpg. No "seat of the pants" change either.

I pulled the plugs on the drivers side, and learned I don't really know anything about reading plugs. Anyway, they all appeared to look pretty much the same. And compared to the photos on the back of the Haynes manual, they seemed to be inline with being okay. But I can't really tell because Haynes has pictures of the extreme conditions. I had a friend scan them, but I haven't converted the images to jpg yet. I'll post them.. maybe you guys could help out with them. Are there any links that give a detailed information on plug reading?

Anyway, this weekend I got some TB cleaner to check for any more vacuum leaks. Nothing as far as I could find anyway. But since I had it, I thought I'd give my TB a quick cleaning even though it didn't looked all that dirty.

After I took it on the road, there was a noticable improvement. What would the TB cleaner have cleaned up that would make such a difference? IAC? Maybe gunk on injectors (even though I have dumped a couple bottles of cleaner in the gas tank for them)?? Just wondering because that may be an area where a more thorough cleaning is needed.

Although it is an improvement, I still don't know if my gas mileage is any better. And performance-wise, it's still not what I'd expect with a 350... but it is definitely better.

 

Oh, another thing that forgot to add: I really gunned it a couple times over the weekend, and you could distinctly smell gasoline. It wasn't obnoxiously strong, but it did stick with me for a while.

 

Have you checked the voltage of the throttle position sensor at wide open throttle? Do that, and see what you get.

spray the throttle body cleaner along the base of the intake... I hear the alumnium intakes are notorious for leaking there.

 

Hey KevinC...What's with the sig man? What do you think these forums are for? I think that it's a little unecessary for a sig on a Q&A message board don't ya think? You'll do what you want anyway, but I'm sure there is a majority that would flame the hell out of that sig if there were a non-tech board on here.

 

Hey lavamadness, just wondering if you found the problem. The first thing that pops in my mind is a clogged cat. If it's never been replaced, I'll be willing to bet that it's clogged.
-Matt

 

Thanks for the reply. Nope, still haven't found the problem. Funny you mentioned the clogged cat matt_at_ttu. I've caught a rotten egg kind of smell a few times. Seems most noticeable after hard acceleration. Yesterday was the first time noticing it though. I'm going to drive around for a bit, make sure it is in fact the car, and see if I can't find a place that'll test it. I'll keep you all posted.

 

Did you check the TPS voltage at wide open throttle?

 

nblanchard, just ran out and did it. (Missed that part of your first post ) Sorry about that..

I turned the ignition to "ON", and jammed a paper clip into the back of the TPS sensor harness, on the blue wire. It read .52v volts without touching anything. At WOT (opened by hand at the throttle body), it read 4.2v. It also increased and decreased smoothly as I opened and closed the throttle plates. So TPS sensor seems okay right? Then I got a friend to floor the gas pedal. It read 3.8v.

Anyone make anything out of that?

 

sounds like a clogged cat to me too.

 

Yeah.. TPS should be good... throw a nice high flow cat on there, see if that solves the problem.

Usually a bad cat can be determined by hitting it with your hand, and if there is a rattling inside the cat, then it is toast.

 

BLM's below 128 indicate a RICH condition, Above 128 inticates a lean condition.

 

I have simiar problems as the above stated. The smell of fuel, sluggish? What gives? I have new cat's and new engine with afr heads. After the installation, the car ran sluggish for about a week and then it felt like it was uncorked...BAM HP! I put my supercharger back on and blew an intake gasket. After I tore down the engine to the heads...I wanted to be sure the head gaskets were ok, so i replaced them too...anyway, once it was back together, it is sluggish again? I programed my chip so my BLMs are @ 128 across the board or very close.

HOw can you check for a clogged cat? I was running extremely rich, however i have fixed that problem and the cat's are new..less that 200mi on them. Really strange because once the engine opened up, it was Freaking fast! Now, it's a slug?

Any help?