I'm getting quite sick of this TPI running not 100%... I dont think its an ignition problem, I am guessing a sensor is malfunctioning/dirty...

When driving the car, there is a noticeable shake, and misfire that doesn't seem to get better/worse with pedal position. It idles fine, and goes into drive/reverse without stalling (most of the time).

Brand New:
Distributor
Cap/Rotor
Plugs/Wires

Engine was timed to 6* BTDC per factory step by step directions after a new head gasket was installed.

Where would you start to look for this gremlin?...

I suspect: TPS is bad/needs adjustment. I just don't understand how you set the TPS...

 

check (ohm) your injectors, just did injectors on a friends car to fix a similar problem

 

How was it running before you pulled the head?

 

Does it do it when you rev the motor in park?

 

I'll ohm the injectors tomorrow!

The car ran good before the head was pulled, it did have a hesitation before accelerating though IIRC. Nothing worth worrying about anyways.

 

I hear your pain, been working on mine since the weather got nice with the same problem figured out it was the 23 yr old injectors. It would idle fine, under load was alot of stalling and hesitaion found both back injectors were leaking and adding fuel all the time. I pulled the fouled plugs yesterday and the old injectors. I get my new ones tomorrow. Remember to Ohm the injectors cold and again hot.

 

Also, for what its worth, I do not throw on the SES light when timing the engine (Tan/Brown Wire unhooked).

 

Injectors Ohm results were determined when the injectors were cold. The intake is all apart right now, once its together (likely tomorrow), I'll check them while hot. I did find that most of the lower intake manifold bolts were finger tight, and one of the runner bolts was less than finger tight. Could any of that have caused the problems mentioned before?...



<--------Rear of Car/Front of Car--------->
Drivers Side:
16.8,16.8 ---- 15.0,16.6
Passengers Side:
16.6,16.6 ---- 16.9,15.9

 

I would replace all the injectors & fuel pump. Preventive maintainence i say. I have to do mines gonna go with a LT1 pump w/dual pickups & stronger injectors since im gonna supercharge it.

 

I thought my bolts were not so tight also when I first took mine apart. I would say its normal. I bet when you get that injector that ohm at 15 cold is going to be alot less hot. I would start shopping for injectors if I was you. You can get a reconditioned matched set for 150 to 200 depending on where you get them.

 

I'll likely buy these. The car is a 5.7 with full exhaust, stock induction. I aldo dont want to change the fuel pressure regulator, or buy and AFPR. Just want to put in new injectors and be done.

http://fuelinjectorconnection.com/sh...&productId=134

Is there any reason not to?

 

Those are the ones I would get, I got those same ones for mine. I hope mine show up today in the mail.....

 

I'm getting pretty good and setting up the TPI system haha, I decided to order injectors if I cant find the "problem".

Got the car running a bit better than before tonight. The power is always there, but seems to get more and less powerful at the same throttle position. Like the power is fluctuating somehow.

TPS Voltage was solid at .55 Volts resting, and about 4.2X Volts at WOT.
Timing was set at 6* BTDC
Wires all correctly installed
All Injector plugs are on correctly


I did not adjust the IAC, or clean and reinstall it
I have not checked for foul plugs (suspecting a lot of bad plugs when pulling them)
I have not checked fuel pressure
I have not checked the Injectors while warm (forgot to before leaving the shop...)

Anything I'm missing maybe?... Could I have ruined the 02 sensor while it was running so poorly for awhile?

 

do all of those items before your throw money at injectors, they may not be your problem.

the injectors you picked are the same ones i just put in my friends car, they work great. he payed 175 shipped

 

Im thinking it sounds like a fuel problem, did you change the fuel filter?

 

Check your tune carefully. Look for damage to a plug wire or any sign of arching through. How old are the wires? Use a spray bottle to spray water on the wires with the engine idling, this will point out any leaks. Check the plugs for carbon tracking down a plug boot. Is it possible you may have cracked the porcelein on a plug during the head gasket job? This type of misfire may not be as noticable at ilde but will worsen when under load.

 

Injector cold test from before:

<--------Rear of Car/Front of Car--------->
Drivers Side:
16.8,16.8 ---- 15.0,16.6
Passengers Side:
16.6,16.6 ---- 16.9,15.9


Injector hot test tonight:

<--------Rear of Car/Front of Car--------->
Drivers Side:
.02,.02 ---- .02,.02
Passengers Side:
.02,.02 ---- .02,.02

Do those numbers seem weird to you?... Checked a couple times on each.

The plugs look incredibly normal, and are gapped at 0.35, timing is still 6* BTDC, all wires are hooked up, and correctly.

I'll rent a fuel pressure tester or buy if I find a cheap one and check that next...


My most noticeable problems while driving right now are:
Backfiring (In the exhaust). Mostly a pop once in awhile during acceleration, and sometimes during deceleration.
Power fades in and out while accelerating and cruising at a given speed, kind of like a light on a dimmer switch if that makes sense...

I am hypothesizing that the injectors are "bad" and giving too much fuel, explaining the weird power fluctuation, and exhaust backfiring.

 

Don't spend you money on anything. You don't need to. Simple problem! Your timing is wrong. What wire did you use to check the timing? It should be only 1 wire near the A/C blower and the color is Tan/Black. Check the firing order of the spark plug wires. Check to see if the rotor under the cap is pointing at the number 1 cylinder at top dead center. There lies your problem. Does your CHECK ENGINE LIGHT comes when you turn the key on?

 

.

 

Noticed something tonight. When first starting the car, and driving immediately, the car seems to run at about 90% of its potential without fluctuation, but after about 4 blocks it will start running bad again. Not sure if that gives anything away, but all info/symptoms help right?

 

Well mine was 2 leaking injectors for sure. Runners were wet all the way to the plenum and plugs were wet and fouled. New injectors fixed my problems.

 

yeah those seem weird, most the time some/all of the injectors will drop from their normal 14-16 OHMs (cold AND hot) to less than twelve when they are bad. Its common for the injectors to ohm OK cold, then drop down to 12, 11, 5, etc. when hot because they have gone bad. getting 0.02 when hot across the board doen't make sense at all... you just got the car hot, turned it off, and ohmed them just like you did when they were cold right?

 

I ohmed them the exact same way as when cold haha. I'll check them again... Them all having almost no resistance would explain a lot though.

 

If injectors are in the 12-13 ohm range, they're shot. If you're getting a 0.2 ohm reading, then they are hooped. Just about everybody benefits from new injectors at this stage of the game. Even low mileage cars are suffering from old injectors. The stock GM Multec injectors don't seem to work too well with ethanol gas.

Is the car hard to start once it's been warmed up? Say after 30 minutes of driving? That would indicate the injectors are running lean and not pumping enough fuel in to start the car (unless you spray starter fluid into it or simply wait several hours for the car to cool off)

Checking the injectors ohms while hot is the true measure of their performance. Many cars will read 16-17 ohms (good) while cold but 12 ohms while hot (bad)

Fuel pressure rarely changes. But it might be worth checking it. It's cheap enough to do.

 

I'd also like to add that cleaning out the IAC valve and throttle body helps a huge amount. It's amazing how much crud builds up in there. And I cleaned mine out after about 35,000 miles on the odometer. $5 can of spray carb cleaner is all you need. Follow the instructions on TGO for how to reset the IAC valve after cleaning it out.

 

What exactly would a dirty IAC cause? I'll definitely try that before ordering injectors.
And, what do you mean by "hooped"? Never heard the term before! Sorry for the noobie questions, TPI is still relatively new to me.

And after about 30 minutes of running, yes the car is "harder" to start. It sort of stumbles to life.

 

it's your injectors, I JUST had this same problem and replaced them. The multecs are crap and don't last too long from ethanol fuel. That one that ohmed out at 15.0 scares me. Also my car would run perfect cold, then like a dog hot and shudder in gear. just a thought.

 

Did you make sure all of the ground wires were connected in back of the heads and tightened? I notice you pulled the heads. It should be 5 ground wires. 3 on the right and 2 on the left or the other way around. One of the ground wires are for the injectors. Another ground wire should go the the firewall.

 

So, nothing considerable has changed other than idling much better, and no more backfiring.

Now it has Bosch III 22lb/hr injectors, fuel pressure set @ 45psi at idle, and a new fuel filter. Still havent cleaned the IAC... I'm pulling my hair out here! Any chance I could have fouled the o2 sensor?

I'll also look at the grounds on the heads/firewall.

All suggestions are welcome!

 

https://www.thirdgen.org/forums/tech...le+adjustmentp

 

Thanks! Was that for IAC or TPS info specifically? My TPS voltage was fine... I'll look into cleaning the IAC tonight after work and see if it doesn't help anything. The only think my book says as far as checking the IAC to see if its any good is how far the pintle is out (1.125").. No way to check with a multi meter?...

 

Do you have any way to datalog the car? Laptop? I would buy a ALDL cable if you have a laptop. Tunerpro is free.

 

I have a laptop, and can obviously download tuner pro. I do not have a cable though, I haven't justified buying one yet :/

Any chance my ECU could have gone bad from the heater core leaking? They are very close to each other....

 

I would have bought one as soon as this went outta my mouth....

 

Point me in the right direction!

 

http://www.aldlcable.com/

This is where I got mine.

 

This is the one to have, correct?

http://www.aldlcable.com/sc/details.asp?item=aldlobd1u

 

Yep works like a champ.

 

Cool, will order it up.. Whats tossing more money into the pit right?


Since this is all new to me at this point, what should I be looking for when I'm running the program? I will be able to monitor and data-log in real time right?

 

Well with Data logs you can find problems and not just part swap to find the problem. Like when I first got my car. It was drinking gas like no other, after plugs, plug wires new O2, cap and rotor button, and setting timing. I found with Data logging that my thermostat was hung open and not letting the car warm up completely so highway driving the computer was running rich trying to warm up my motor. Now I know the other stuff needed done but data logging saved me alot of time as the stock gauge is not that great.

 

12 pin ALDL cable is coming in a couple days, and Tunerpro5 is now on my desktop. Now I play the waiting game...

 

The mailman is your new best friend......lol

 

Yeah... and he better hurry his lamborfeeties up....

What else should I be looking at in the meantime!

 

first thing to do is pinout test on ecm knock sensor outpt could be bad

 

Post #17 indicates failing injectors. Or your ohmmeter leads were crossed when you hot tested. Look for Block Learn to go high, indicating a lean condition. That would support the injectors being your problem.

 

He replaced the injectors.... post #29. I am getting him setup to datalog to see if it is running lean or rich. He pulled his ECM to look and see what chip was in it and found a Hypertech chip. After looking on there website I see they only want you to run High octane with there chips.... He might be getting spark knock from the aftermarket chip that has been running his engine against the knock sensor. Im not sure what octane gas he has been running. Maybe the knock sensor is bad.

 

.

 

Got the log looks like the Hypertech chip is part of the problem. Something is making the ECM jump around. He pulled the Hypertech chip and put the stock AUJP back in and it was idling alot better. heres a pic of what the log was showing.

 

I could've told you the hypertech chip made the car run worse. My car ran terrible all around with it. Once you get your tune dialed in you'll be surprised how much the car had in it.

 

Well, we didn't know it had a Hypertech chip in it til last night, thanks though...

And I hope I'm pleasantly surprised... lol