Dustin Mustangs

iTrader: (1)

As some of you might know, my roc has been giving me some trouble for a while now. I decided to take some time and put together a post that tells the whole story in hopes that someone might have some ideas for me. Some people, my dad mostly, say this car runs fine (he doesn't know $hit about cars that don't have a carb), but at one time it was definatly faster and more efficient than it is now. This was a gradual decline in performance and economy over time, nothing quick or dramatic. Here are the symptoms:

1.) A lope at idle - this is a small lope, you can see the tach move +/- two needle widths. It happens wether the engine is warm or cold, open or closed loop, all the time.

2.) Sub-par power - this is hard to explain in any more detail. It can still put u back in the seat, just not with the ease that it used to.

3.) Crappy gas milage - I get around 200 miles to the tankfull, 225 max if I'm on the highway. I can remember getting 270's easy when I first got the car.

4.)BLM's at 132 - thanks to my half hearted scan tool, I can only get a reading at idle, which this is. It does also show an active O2 cross count.

5.) Hard starting - this is the newest of my symptoms, begining just recently. What I mean by hard starting is, never does it fire up on the first crank. Untill just recently you'd just have to blip the key and it would come right to life with a slightly higher idle, and then slowly settle down to say 650rpms. Now, I'll crank it, it'll give me a sputter which tells me to let off the key to let it fire, and it just dies. Most always it will start on the second try. This also happens regardless of engine temp or loop status. Some times when it has been running for a while and is warmed up, and then shut down for a few min., it will have even more trouble starting. It will do the same thing as before but when it does start the idle will stutter at about 500rpms and feel like it could stall at any second instead of shooting up to higher rpms for a short period like it usually does.

It has no codes stored and my scan tool shows nothing out of the ordinary other than the BLM's, I think. Most of the more common things to check with symptoms like this have been considered. Here is what I have done so far. It has good vacuum(17"), the timing is set at 8`, the FP is at 50 psi, and the TPS is at .58. ALL of the 'tune-up' parts you can think of were replaced recently when the new engine went in. Also, the CTS, the O2 (I went heated for the headers), and the ignition module have been swaped recently. My injectors are whithin 1% of each other and 'as clean as a whistle', according to our good freind Rich. My sig has all of the non-stock parts I have put on. The jasper engine now has ~5000 miles on it, and burns no oil. The tranny also recently has been flushed by a freind. The fluid looked ok and no noticeable differences in how and when it shifts.

This is what I have so far. I currently question my egr valve the most. I think it might be hanging open, but as far as I know there is now way to test for this. I would just thow a new one in, but I am sick of installing new parts with little or no improvement, not to mention it's about $80. I also am considering that the new engine might be sour, but I can't say I want to do a compresion test in such a tight engine compartment. Anyways, any internal engine problem could be noticed by oil consumption? Please post any thoughts, opinions, or theories on what could be wrong with my sick roc.

thanks for any help:hail:

JAY87GTA

Have you checked the fuel pressure while driving down the road to ensure you're getting the volume of fuel you need? Also is the fuel pressure bleeding of rapidly after the key is turned off? A faulty regulator or maybe pump comes to mind as causing the hard start problem, and will also cause the drop in power. Later

TPI Monte SS

I had noticed the same thing with my Monte SS, over a period of several months. After doing the basic tuneup stuff (plugs, cap & rotor), and cleaning my K&N cone filter, I still felt the same way.

I brought the car to my job yesterday and had them change the fuel filter. I've driven the car about 15,000 miles since we swapped the TPI in, so I figured, "Why not?" I took the car home during the day, and didn't notice much of an improvement, but it was 95* out. After it cooled down last night, I went out for a ride, and all power has been restored! The car is its evil old self again.

Even if you changed the filter 5,000 miles ago when you swapped motors, it could be due for a change, depending on how long the car sat before you completed the engine swap. Lots of junk can build up in the gas tank.

Ed Maher

Sounds to me like a combination of a vacuum leak w/ too much FP on a stock chip.

Dustin Mustangs

iTrader: (1)

Thanks for the replies fellas. As you all mentioned my fuel system could be suspect.

Jay: My pressure no dought holds steady for a long time after I turn off the key. Rich also told me that my injectors held a seal at 80 psi with out a problem, although he didn't get to check my cold start injector. I have not tested the presure under load yet but I plan to do so, I'll get back with the results. I forgot to mention this before, but I have tried all differnet octanes and am currently running premium. On a similar note, I noticed that when I turn my key to the on position, without engaging the starter, when my FP primes itself it doesn't go as high as it does when it idles, mabye 10 or 15 psi less. Is this normal?

Monte: I dought it is the fuel filter, but with how cheap and easy they are to install, F- it, I'll throw another one on just to be sure. The car didn't sit for more than a week for the engine swap, but it does go out of commision every winter for about 5 or so months.

Ed: My gauge reads my FP at 50 psi, which is what most recomend around these parts, with the vacuum line disconected. I actually think it might be closer to 47 psi because the stock regulator with the same gauge read 47 when it should of have read 43.5 psi, right? Also, I can't imagine I have a vacuum leak. First, I have beaten the old 'spraying carb cleaner test' to death about 3 times to no avail. Also, this problem has stayed with me through dis- and re-assembly of my TPI a number of times and continues to remain constant.

Keep the ideas flowin' guys, they are much appreciated!

Ed Maher

Well, you need to figure out if your FP guage is accurate or not. If it's not (i.e.e stock pressure should not be 47), then it's kinda hard to know where you're at now.
As for actually running 50psi, most that recomend that around these parts would also think that a 305 running 14s was impressive. People who actually KNOW what they are saying will tell you that fuel pressure must be matched to injector constant and what the car wants. It;s not a set it and forget it thing. You should know this much though if you're running a scan tool.
Which leads me to your BLMs. If your fuel pressure is bumped and you're still getting 132 BLMS at idle, something is amiss. It's either:
1- you have a vacuum leak
2- you have an air leak on the drivers side exhaust skewing the O2 readings
3- you have a/some weak injectors on the driver's side
4- your maf is on it's way out.

You know that your injectors are good, so i'd make sure to triple check the others above before you ruled them out.

Also, 17" of vacuum in car with a stock cam is borderline low. If *my* car was only making 17" of vacuum i would consider it a symptom of a problem. A problem like a vacuum leak on the driver's sdie runner, amking that side show lean, making the ECM add more fuel, making the pass side run rich, making the engine run a little less smoothly, thus giving you only 17" of vacuum and a lopey idle. Likewise, this vacuum leak will also constantly be skewing your O2s in light cruise, killing your gas mileage.

99Hawk120

17" is a little low for a stock-cammed TPI car. As a data point, I'm pulling 17-18" on my ZZ4 cam.

Ed Maher

With a carb to boot (i.e. EFI should make more)

99Hawk120

Ed's correct (again). I forgot to mention my car was carbureted. The last stock TPI car I measured the vacuum on pulled almost 20".

Dustin Mustangs

iTrader: (1)

Things are still on the decline. I just got my lowest mpg ever calculated; 11, which even included some highway. I am in desprate need of help, my wallet is shrinking and the Mudstains are starting to circle.

Ed - Things are looking like you have me headed in the right direction. Fact is, I have been annoyed with a noise I have come to associate with my headers. For some reason I decided to rump-wrangle myself with the 50 cent paper gaskets that flowtech supplied with them and they've probobly been leaking ever sence. Looks like it's time to do it right with some percry's 'dead soft' gaskets and stage 8 locking bolts. I can't say I'm looking forward to that task, but it will give me a good oppurtunity to check and change the dreaded spark plugs.

I have noticed that my BLM's aren't behaving quite as I said before. I started paying more attention when I found them at 126 idleing in the same driveway that I found them at 132 last time I checked. Crusing back from girlfreind's house, ~45 mins @ speeds of ~75, I checked them just after I got off the high way. They were over 140 and steadily droping down to 128 by the time I got to my house, ~5 more mins @ speeds of ~25.

This seems to verify the header leak diagnosis, doesn't it? Also, I noticed my BLM's will go up a few if I give the throttle a slight blip in neutral. Is this normal? I thought they were supoposed to be the 'long term' correction factor. Mine seem to be responding on more of a short term don't they?


I'm not worthy:hail:

Dustin Mustangs

iTrader: (1)

nobody's got nothin' for me?

Ed Maher

The blip you're seeing in the BLMs is most likely from changing block cells, there are 9 stored BLMs covering a 3x3 of low-high rpms and low-high load. When you rev it, or change load, you change cell.

I'd like to see you do the header gasket before you worry too much about anything else. And doing a good check for vacuum leaks and loose TPI bolts is a good idea too. You'd be amazed at how much little stuff can absolutely kill you in these cars....

Dustin Mustangs

iTrader: (1)

Ed-

Your help on these problems is really appreciated. In fact, all of the moderators on this board deserve some props for making this such an informative site!

It's probobly gonna be a couple of weeks for me to get the stuff I need to redo my shady-tree header install. I'll let you know how it turns out.

Cheers