Hey Guys,

I am having some problems with my car and am in need of some help. My car has the following problems, no response when throttle is given, I floor it and nothing happens. This is an intermittent problem that happens at low and highway speeds. It has also developed a terrible idle, it searches for about a minute, and then it is fine. Sometimes the idle jumps to 1200-1400rpm. I have scanned the computer and the following codes came up: 25, 33, 34, and 42. I have replaced the pickup coil on the distributor, both MAF power relays, the TPS, and the coil wire going from the coil to the distributor. The car is still behaving poorly and seems to be getting worse. When it acts up, I can smell the car running very rich.

Now, two days ago, I bought some CRC MAF cleaner and cleaned the MAF per the directions. I sprayed the MAF in both directions and let it dry. I reinstalled and took it for a ride. The car ran great! No idle problems, no hesitation, no power loss…for about 20 minutes. Then all the gremlins came back.

I’m really lost here and looking for help. I just bought the car and don’t want to dump the money into a new MAF and have the problems reappear.

Car Info:
89 Formula 350 TPI with an Auto
Engine was rebuilt about 20K miles ago.
355 CI w/ L82 camshaft

 

could be the idler. about a $100 part

 

MAF burnoff relay, unless you already checked that.

 

I have replaced both MAF relay's, the power and the burn-off.

When you say idler, are you refering to the IAC or the idler pulley, or something completely different?

 

Have any of the codes gone away since you replaced those parts?

Unhook you battery, wait 30 seconds, reconnect the battery. Go for a drive and check for codes again.

Did you adjust the TPS correctly?

Can you check fuel pressure?

 

No, the codes have remained. I have disconnected the battery several times (overnight) and the car still runs like crap.

The new TPS does not have an adjustment screw.

Can I check fuel pressure from the schrader valve on the fuel rail?

 

the tps itself doesnt, but the mounts are slotted. You can loosen it and rotate the whole unit. That is how you adjust it.

 

move the mafs terminal around and see if it runs any better

 

Alright, I adjusted the TPS to .54V and it reads 4.83V at WOT. Took it for a spin, very noticable difference. Ran great, idled fine, and burned the tires from a 20mph roll. It was still a little hard starting, but it could just be the cam and the need for a tune.

I re-set the computer (unplugged for 2 hrs) and took a ride and the issues came back...poor idle, hesitation at low speed, etc. I shut the car off, fired it up 3 minutes later and it ran great.

Any thoughts...

 

When the car is running like crap, try disconnecting the 4-wire connector on the MAF. See if it runs any better. If it does, replace the maf.

 

Sometimes a bad MAF will also so symptoms when impacted. When it's running great, lightly smake the MAF with a screwdriver or something. A bad MAF will often stumble.

 

I have tried jiggling and moving the MAF connector around as well as smacking the MAF with a screwdriver and nothing would make it stumble.

It seems like it will only run like crap in open loop now, after I adjusted the TPS. I am going to try and clean the throttle body and I would like to check the coolant temp sensor. Does anyone have the resistance values for the coolant temp sensor? Perhaps also the values for the Manifold air temp sensor?

 

https://www.thirdgen.org/forums/atta...ase-ctsmat.gif

 

Ok, so after taking some notes, my problem seemed to only be a problem on startup and driving in open loop. I check the resistance of the coolant temp sensor and it was way off (~21,000 ohm which is equivalent to 0*C). Bought and installed a new temp sensor and while I was at it I cleaned the TB, well the car ran great for like 3 days. Then I go to drive it on the fouth day and all the old problems came back, hesitation above 2K, poor idle, running very rich, no power, etc. Try it the next day and its fine.

I finally got my X-ray scanner to read the ECM (had to tell the Xray that the car was an 87 with a 350) and everything appeared to be normal, except the MAP sensor. It stayed constant when I was on and off the throttle. So now I have a new set of questions, first being where is the MAP sensor located? What is the MAP supposed to read at idle and part throttle? Is there anyway to do a resistance/continuitity test on the MAP sensor? Why doesn't AutoZone list one for my car on their website?

Thanks in advance.

 

I thought you had a MAF based car. They are mutually exclusive in our cars... obdII cars often have both, but not us.

 

Interesting...so because I have a MAF, I do not have a MAP sensor?

Something else of note, the car started running like crap again today, the MAF was not responding. It was stuck on 40g/sec. I pulled over and tried tapping/shaking the MAF, it did not run any better. Would the MAF be causing this intermittent issue?

 

do I type for my health

just buy a new one

if it is too expensive

trade your car for a carb ride

fuel injection is expensive no matter who or what you know

 

So my car ran great for about 40 miles today, then I started it up while it was still warm, and it ran like crap. This time, I shut it down and unplugged the MAF. The problems went away completely and the car ran great. Something interesting though, according to my X-ray scanner, the the MAF was still registering, the flow rate was right on par with the throttle position. I am thinking that the car ahs some type of static MAP or some other reference to barometric pressure, combine that with the TPS voltage and the computer is then calculating the mass air flow from those two readings. FYI, two days ago the MAP sensor was reading 2.42mV through the X-ray, yesterday it was 2.80mV.

I have 3 more days to get this car through emissions, I am thinking of dumping in a couple gallons of methanol and going through with the MAF unplugged. Thoughts?

 

That is interesting. I have never heard of these cars having a MAP sensor of any kind in a MAF car, but I have been wrong before

 

Well guys, summers back and so my car is having problems. First, some things I have done to the car: new Battery, manifold air temp sensor, EGR valve, positive and negative battery cables, checked/cleaned all grounds, checked injector resistance (15.2 ohms for all), pulled a couple plugs and they look good.

My problems revolve around starting the car. Cold start it will crank and crank for about 20 seconds before it fires up. It helps when I give it a little gas when I'm stating it. Hot start it won't even crack, just the starter solenoid clicking it all I hear. The car runs great once its started. I am thinking that the two problems are not related as I'm thinking the starter is the cause of the hot start issue.

Any thoughts?

 

Forgot to update this, I replaced the MAF last year and it fixed everything. Car runs awesome now...and it is for sale.

https://www.thirdgen.org/forums/fire...ml#post4682735