Duane's 91 Z/28

iTrader: (1)

I got my engine all rebuilt and put together. I got it running and it has somewhat of a rough idle. I replace the fuel pump, filter, all the sensors except for the TPS and IAC. I took my car back and forth down the driveway a few times and I tried to get on it and it spit and sputtered. Brian @ Tuned Performance tuned my ecm and it's fine. No check engine codes. No black smoke or rich smell out the exhaust My fans come on when they are supposed to. I didn't touch my injectors or fuel pressure regulator. I haven't checked the pressure yet or ohms (don't have an ohm gauge).

Duane's 91 Z/28

iTrader: (1)

Oh yea and it has all new wires, distributor cap, spark plugs (R45TS) and engine control module.

Tuned Performance

iTrader: (92)

Are you using the stock multec injectors. I will be more than happy to read the programing again but I'm pretty sure the issue is somewhere else. It was a pretty basic tune. Not saying I don't ever make mistakes but I'm never wrong just mistaken lol

Duane's 91 Z/28

iTrader: (1)

Yes I am pretty sure they are stock. They are grey in color and looked old. I don't think the ECM is the problem, Its something else. I will see if I can get an ohm meter and check the injectors. I'm not sure how to check them. Do you just pull the plug off the injector and touch the connectors?

Tuned Performance

iTrader: (92)

Your ight with the engine warm you can ohm the injectors with ther connecter unplugged. 16-16.5 is a good coil reading +/- .5 . If any are 12 or lower they are junk. The Multecs coil coating breaks down and they short out with ethonal fuel. This will just test the coils. the only way to check the flow is a pressure drop test or have them serviced. I wouldn't wast a dime on Multecs.

Duane's 91 Z/28

iTrader: (1)

Mine are the Multecs for sure. Maybe I should just invest in the Bosch injectors. How can I test my fuel pressure regulator in case I need to replace that?

Tuned Performance

iTrader: (92)

I would replace the crossover o-rings on the fuel rail as well. To test the regulator prime the fuel system with turning the key a few time and watch the fuel pressure. It should stay steady at 43.5psi and take 8-10 min to drop. Southbay has them for a good deal while your in there.
http://www.autozone.com/autozone/par...ier=79645_0_0_
http://www.southbayfuelinjectors.com...tpi-injectors/

http://www.southbayfuelinjectors.com...tor-diaphragm/

Duane's 91 Z/28

iTrader: (1)

How do I know I got my wires hooked to the right injector on the engine? They weren't hooked up when I bought the car. I put them in the injectors the way they were bent around. I moved the wires to the opposite injector and it didn't seem to make any difference the way the car ran.

Duane's 91 Z/28

iTrader: (1)

Well, I went out and checked my fuel pressure. It was 42-43 psi but right after the fuel pump went off it dropped right down to below 20 psi. The regulator is total junk. lol I am surprised my car even runs.

Tuned Performance

iTrader: (92)

To tell for sure if the pressure is dumping out the return, you can use a pair of vice grips on the rubber flex line that jumps from the frame to the engine. The hard line is the smaller of the two the 5/16 . Use small pieces of wood like a paint stir stick between the jaws of the pliers. . Prime the fuel system and clamp off the return and observe the fuel pressure. If it drops the is a few places the fuel can go. leaking injectors , through a ripped fuel pressure diaphragm (pull off the vacuum reference line and look for signs of fuel ). Or it can leak back through the pump or pulse dampener. I always toss the line dampness. it causes more noise in the fuel line but one less area to leak and fail.

Mike 92LX

iTrader: (6)

FIC has cheaper prices on those than Southbay

Duane's 91 Z/28

iTrader: (1)

I got the Bosch injectors and Fuel pressure regulator and diaphram and got them all in. I don't have everything else hooked up so it can run yet. I checked the fuel pressure and it still does the same thing. Goes to 42 lbs and then drops off after the pump turns off. No leaks at all this time around (after I pulled the fuel rail and reset the injectors because of an o ring got into the fuel rail and I went and bought new o rings just to be safe) I pinched off the return line also to see what would happen and it still leaked down!

Duane's 91 Z/28

iTrader: (1)

I cant seem to find any answers to my pressure problem. I think I am just going to put everything back together tomorrow and see what it does. I beginning to think there is not any problems with the new injectors or regulator.

Linson

rough idle can be an indicator of a vacuum leak. other indicators may include poor brake performance and high idle speeds. have you vacuum tested the car? you can also isolate a leak by spraying brake cleaner or similar around the engine and listening for a change in idle (usually it will surge if there's a leak.) the TPI runners are the most common area prone to vacuum leaks.

Duane's 91 Z/28

iTrader: (1)

Thanks Linson. I'll see how it acts when I get it back together today then go from there

vdoggie

I'm going to assume and correct me if I'm wrong that even if all my injectors are testing fine at 16 anyone of them could have an uneven spray and something that could cause a mild rough idle or some gas leak in the system somewhere? I ask because every time my car stalls at low idle or coming to a stop, backing up, putting it in gear after idle, once I restart the car, it smells like gas.. and it doesn't help that the car runs way too rich and I can't figure out why..

For whatever reason I think these symptoms have to do with the injectors and or something in the whole fuel/tpi system.. can anyone suggest some other simple tests? o2 maybe? I'm not getting ANY codes from the paper clip test in the odb connector.

JacobIroc

So. I didn't read the whole thread. However, when I did my 305 TPI swap into my 92 RS, The alternator was garbage. It caused the engine to run like dog ****, would be worth a few minutes to put a multimeter on it.

vdoggie

Yeah I could check that.. I definitely have some issue with the key/ignition/vats because sometimes when I turn the key it doesn't do anything and I have seen this on both keys.. but this is a different issue all together.. these are really my only primary issues.. otherwise the car runs fantastic and is still strong.

southbay08

If you want to see if one of your injectors are leaking, run the engine and then pull the plugs. If you have a wet cylinder you more than likely have a leaky injector. Check your regulator diaphragm as well.

Johnny Blaze

iTrader: (15)

Vacum leak?
Base timing setting?
Properly set the tps?

What changes were made during rebuild, cam, compression ratio, etc?

vdoggie

I will have to find out where the regulator diaphragm is and check that out.. thanks for the tip!

vdoggie

Well I just found out that the original 305 memcal is still in the ecm .. and I'm pretty confident it was never flashed because it certainly wasn't removed.. unless they did the UV light erase method.. I doubt it by a country mile or two they didn't. I think this will have significant impact on the symptoms I'm having. The only thing that is curious is, wouldn't a 305 chip in a 350 engine make it run leaner versus running rich???

The thing is, I don't know anything about this engine swap but it looks stock to my mechanic.. thank God he has an original 350 ecm with the 350 memcal from his 1988 iroc-z!!! I'm soooooo lucky he is going to bring it in and hook it up.. I already have the damn thing hanging out on the passengers side.. lol

If anyone else know what symptoms using this 305 chip in a 350, please let me know so when we replace the ecm there is a chance they might have compensated somewhere else in order to have it run good enough.. could they have jacked with iac, tps, timing or other??

Johnny Blaze

iTrader: (15)

Any idea what year the engine is? What about the cam?

There are many varibles that could cause issues.

vdoggie

I have an engine block number 14064535

However I can't seem to find relevant information on that #

My mechanic got it for me and had to use some scope to get it as you can't get the proper angle with the naked eye. Is there another location I should be looking?

I'm about to check idle rpm's and timing..