Mark L. Warner

Here are the vitals; '88 l98 (355 now), miniram, zz9, 52mmTB, ported alum heads, 10.25 compression, dual exhaust, cold air induction, stock injectors, GN fuel pump, MSD, TPIS Level VI PROM, etc. It is still running rough at idle, and it wants to idle at 750 - i think it needs 900-1000 rpm. Engine shimmies when idling, and vacuum needle shakes between 15-16" sometimes dipping to 14". I have re-set the timing to 10-12 BTDC and that has helped a little bit with the off-idle hesitation, but it still runs rough. It also runs rough through 3000-4000 rpm with little missing sounds. It just still seems "off" or something. I have checked all the fittings looking for vacuum leaks though I did not use a stethoscope or propane. I don't think the cam was "degreed" when installed - how much can I play with the timing to help compensate if the cam is not just right? I am really at a loss here and I coul really use some help! :banghead: :mad :confused:

jerkyboy

Again Mark, you really need some wideband O2 readings from a Dyno to see where your A/F ratios are at different rpm ranges. Don't assume the TPIS chip is correct. Sounds like you might be rich in the middle. I am working through the same issues now.

Aggravated4life

Another Idea,but unsure if it would help much...did you set the minimum air speed on the TB?Then what about the TPS voltage?You may even need to adjust the minimum air speed to a rpm the engine likes to run,then set the TPS voltage...maybe kinda experiment.If it was me,id run the stock TB first and see if it runs any better.I tried a larger TB and it ran poorly and the idle hunted and so forth.had to adjust the minimum air speed and set the TPS a few times until I found that sweet spot.Dont forget,if you adjust the min. air screw too far off and the TPS,youll get a code 33 from the MAF which would be an unrealstic airflow at certain rpms,not that the MAF is bad.

But like the other post said,you may also need to check the o2 readings and see if theres something off there.
:)

LD85

Check the base of the intake to the top of the block for leaks, you can do this buy pumping up the block with air from a foot pump and listen for leaks. I had a leak there and never knew it till Ol'RJ did a pump up test.

Reset your IAC and TPS to @ .590-.600 so that it does idle at 850-900

JAKE

Where are you taking the vacuum readings? I take mine from the little hose bib on the power brake booster.

I use to run a ZZ9 with 1.6 Pro Magnums in a 355 and it pulled a steady 15" of vacuum idling in gear. The ZZ9 is a relatively mild camshaft.

I'm gong to assume that no plug wire is crossed or burned and are in good condtition, spark plugs are gapped properly and in good condition as well as the distributor/rotor,coil, etc.

A flucuating vacuum gauge with a drop as you reported makes me suspicious of a vacuum leak. You should first eliminate that possibility. Try pouring water all over the gasket sealing surfaces with the engine idling; if the engine stumbles you've found your leak.

Are you positive the lifter preload is set properly? A tight adjustment will cause rough idling.

Once all the mechanical/electrical possibilites are checked, you'll need to capture the data the engine is seeing as it runs. Diacom or a ScanTool will be needed to show all the values the ECM is seeing/commanding.

Idle speed is determined by what's burned into the PROM, so to raise the commanded idle speed to a higher rpm, the PROM will need to be modified. You could open the TB butterflies to get that rpm, but the IAC would no longer be able to control idle speed. That's really not the way to do it. The ZZ9 does not need an idle speed of 900-1000 either; 750/800 is plenty. So since you posted that you think the engine needs 900-1000 rpm idle speed, that tells me that something else is wrong in the engine. Could very well be the vacuum leak I suspect.

TPIS use to offer two re-burns of their PROMS for free, but in order for that offer to be of any real benefit they'd need to see the actual values of the running engine (saved to a floppy or emailed to them). Idling, part throtle around-town driving and WOT data. Otherwise, they'd be shooting in the dark.

Hope this helps, keep us posted.

Jake




[Modified by JAKE, 12:16 PM 12/1/2003]

Aggravated4life

I wanted to add I agree with Jake about the TB...I reread my post and didnt want to appear I was saying to manipulate the TB by making it idle higher...the problem is alot of larger TB are not preset at the factory in position like say the OEM's are.. and alot of modified engines may not run the same with the TB set in the same position...and you need to set it just right to run right as well.Turning the blades all the way out is not the answer.Sorry if it sounded misleading.

:cheers:

JAKE

So true. I just went through this a few weeks ago when I installed a new 52 mm BBK TB. I took me several days and lots of different adjustments to the TB butterflies before I found the sweet spot for my combination.

20 to 30 counts is the recommended reading for the IAC motor, yet when I set it to that range, the engine would not idle down when I lifted my foot off the accelerator pedal on the roadway. The rpms stayed up and the car wouldn't slow down.

So I had to close the TB butterflies a little at a time, which made my IAC counts go higher.

The final setting left me with counts in the 65 range, but now all works well.

My PROM is programmed for 800 rpms, idle in gear for the cam I'm running now. When I had the ZZ9 in my 355, if memory serves, I was using a different PROM and it had it set for 750 rpms. The engine idled extremely well with that RPM setting and an 89 bin file.

I've read a lot of comments about how awful TPIS PROMs are. One story is that the guy who use to burn them was a real guru and did an outstanding job, but he left the company for some unknown reason. The person(s) who now burn(s) them isn't/aren't as good at tweaking their standard programming. Just what I heard.


At some point it's going to be necessary to have a 'look see' at what's really going on with the engine; meaning Diacom, ScanTool or some other program that will give you real-time data while the engine is running. Absent that data, there's no way to really know how the PROM programming is working with your particular combination and/or any other readings that may be out of spec.

Hope this helps.

Jake





[Modified by JAKE, 3:07 PM 12/2/2003]

Mark L. Warner

Guys, thanks for all the input, I will keep everyone posted. That's why this forum is the BEST - because you guys ALWAYS come through. PS - Jake thanks for the e-mail!!!

ol,RJ

I'll second the "rocker arm adjustment".
a fluctuating vaccume signal with an rough idle (and other rough areas in the rpm band) points to something out of sync.
If it was a constant vaccume leak (like a vaccume hose off) it would run normal at higher RPM (lean but consistant).
another possible cause is a bad sparkplug or plug wire.
even a brand new sparkplug can be bad, and heat can effect the plugwires resistance even if it still looks good on the outside. If you have any plug wires that are real close to a header pipe I'd check them first.
RJ

MITCH

mark i have the same problems with my car off idle and between 3000 and 4000 my car is a 422 mini ram my idle is great at 850 . i been try to get this fixed for a while.my car is runs better cold than in the hot weather.
just to let you know you are not the only one. in my opinon tpis chips are the worst and there cust service sucks i have spent a lot of money over the years with them and they have been no help. :mad :mad
mitch
speednut2@aol.com

MITCH

top

JAKE

You'll need a file of all the data readings in three modes.

Cold start idling (Cold start meaning when the car as sat overnight)

Around town and highway part throttle and

WOT Blast

Diacom is excellent for this. You can set it to the record mode and accomplish all three tests; then save them to a disc. Send the disk to Ed Wright along with your PROM (or buy a new one if your budget can stand it).

It would be great if you had the Diacom program or could borrow it from a friend for the short time it would take to run and save the tests. If not, TPIS use to rent the program and the connectors on a weekly basis.

To get the programming as close as possible, the person who tweaks the PROM will need to see the data on what's actually going on with the programming you are running now. Anything less is just shooting in the dark or best guesstimate.

From all I've read, Ed Wright will work with you to get it right. He comes highly recommended by all who have used his services.

BTW, I agree with the assessment of TPIS Level whatever PROMS; I believe they're generic. I had two of them and they were awful.

Just my opinion.

Jake



[Modified by JAKE, 3:40 PM 12/3/2003]

88_vette

Yeah I'd have to go with the TB first. The BBK if that's what you have has been known to cause idle issues. I had one that didn't have the idle air passage machined well and it wouldn't allow enough air to flow. I also found other's that had this problem. Now this was a few years ago back when they first came out. Not sure about these days. I have a pic of what I'm talking about. I will try to e-mail it to you. Also this is a last thing to check but it maybe you need to have some major tunning. When I built my 383 I couldn't get anyone to burn a chip to make this thing run right. All were mail order. I tried two different places and sent back several times. Finally the cost of the chips and shipping was getting to be more than burning my own. So I conv. to the 730 SD setup and the car ran better off the first burn then it had ever run. I have since tried to burn and use the stock MAF setup, but I can not get it to run right with the MAF and 165 computer. NO matter what it just runs like crap with the 165 ECM. Point here is you have a 88 with semi heavy mods and are running into the same issues as I did. Which turned out to be mostly ECM related. This is why I said you may have to find someone that can look at your car hands on. Again I would rule out the other great advice given above by others first.

Mark L. Warner

I am totally unfamiliar with the "730 SD" is that some kind of aftermarket ECM that you can buy? Please give me more info. Also, did you end up burning your own PROM? How do you do this? I would think that setting up a PROM based on a certain set of mods would be simple but I guess not. LAstly, I DO have the Edelbrock BBK 52mm TB and it is about 1 year old. I never really noticed any restriction problems with the idle air passage, what should I be looking for? Thanks.

JAKE

Here's what I'd do.

Initially I make absolutely sure that all the vacuum lines are connected and none are leaking, perhaps cracked from long exposure to heat. Check that there are no hose bibs left open.

I'd make sure that no lifter has too much preload, which would cause the valve to remain slightly open and result in very rough idling.

I'd check to make sure all the gasket sealing surfaces are tight and no vacuum leaks are occurring from any of them. The old squirt the water trick.

I'd make sure all the plugs are firing, all plug wires are properly connected and arc free (can be checked in a darkened garage) and the boots are in good condition- none touching the exhaust.

I'd set the TB minimum air flow (using the little TB screw) to get the IAC counts in the 30 to 40 range. You may have to settle for higher counts, as I had to, like in the 50 to 60 range when using a 52 mm TB.

I'd set the TPS voltage to .63 with the engine idling. I know, the procedure for setting it calls for the engine to be "off" and the ignition key to be "on", but I got the best results setting it with the engine idling.

I'd raise the fuel pressure to 46/48 psi vacuum line "ON". I know this is higher than you normally read about, but you can always begin lowering it to fine tune the adjustment. I'm running 48 with 26# injectors. I tried lots of different settings and the engine responded best with 48. I let the engine tell me what it wants and likes.

With fuel, it's better to be a little too rich than a little too lean. With spark advance, it's better to have too little than too much.

Remember, the recommended procedures for doing some of the settings is for a stock engine, once you modify it as much as we have, some of those procedures don't work as well. I only recommend this because it worked for me.

I'd set the initial timing to no more than 8 degrees BTDC, with the EST connector disconnected, engine idling at 800 RPM. If you set it higher than that, chances are you'll be getting a lot of timing retard and knock counts, especially with 10.25:1 and a ZZ9. Be sure to clear the error code that gets set when the ECM detects the EST connector disconnected.

If your cam had more duration you could probably get away with bumping the timing 2 more degrees or so, but the ZZ9 is a relatively short duration camshaft and will build a lot of cylinder pressure at low rpms.

I'd make sure the engine is going into closed loop and that the 02 sensor is very active; meaning that it's crossing the 450mv range repeatedly and quickly with cross counts steadily climbing, faster than the second hand on a digital clock.

I'd make sure my BLM and Intergrator are within 8 of the nominal 128, meaning no more than 136 and no less than 120. 6 would be even better.

Fuel pump voltage should be at or very close to 14 volts.

I'd make sure that the idle air GPS are at about 7 grams per second and injector pulse width is at about 1.7/1.8 ms at idle, closed loop.

I'd check to make sure the engine idle speed is maintained no more 75 rpms higher than the desired idle speed, but not more than 25 rpms below the desired idle speed. If the PROM desired idle speed is burned in at, say, 800 rpms, that would me no lower than 775 and no higher than 875.

Make sure that the ECM Learn Function is "on" during closed loop operation.

It's really difficult to diagnose some problems over the internet; we do the best we can though.

Hope this helps.

Jake




[Modified by JAKE, 4:22 PM 12/3/2003]