94 Quad 4 starting/idle problems

[3X00-Modified]

They make Wideband O2 sensors just fine.

Also something CAUSED your converter to plug up which could be the source of all the problems... just replacing/removing the converter doesn't fix it. You could have a fueling or spark issue that caused unburnt fuel to get dumped into the cat and then clogged it... so just remember that. And yes that could be from the o2 sensor as well, so after replacing it just make sure everything else is running top notch otherwise you may get a plugged cat again.

[BadBerettaZ26]

Well my cat shouldn't clog up again, I punched it out weeks ago when i first discovered it was plugged.... it had broken up inside and the bigger pieces plugged up the outlet.... but i agree, something had to ruin the cat in the first place.

I changed the O2 sensor today and it didn't make hardly a bit of difference.... CEL still comes on one minute after startup and it still stumbles and misses randomly while driving... I can floor it and itll go but with normal throttle usage while cruising it still does it. Still running rich as well. What next? I shoulda just went today and checked the codes but i spent my time changing the sensor thinking that had to be the problem...

[spacecadetz26]

check your coils hot and cold. also check the wiring for the coils. and see if your canadian tire can test the ignition module. and ohm your fuel injectors to see if they all match. one bad injector can do all kinds of crazy things.

[SuzukiGhostRider]

1. Ohm out coils.
2. Test ICM.
3. Test TPS
4. Test fuel pressure to see if you have a bad pump or not.
5. Ohm out your fuel injectors.

One of these (or more) will fail and tell you the issue that needs resolving.

Your Cat failed because it was almost 20 years old and crumbled apart. Can't imagine WHY that might happen at almost two decades old....

Happens in most 20+/- year old cars.

[spacecadetz26]

testing the fuel pressure requires a special tool something most places dont have either, unless you make one or order one online. its just a quick connect that plugs inline to the fuel line and has a schrader valve to test the pressure.

[spacecadetz26]

i found a pic

[3X00-Modified]

Depends on the quad fuel rail used too. Pauley's quad has a shrader valve right on the rail, Patrick's doesn't. Go figure.

You can see the brass cap on his FPR



And SGR I would agree with you on that one if he did not have this missing and ill running issues after punching out the cat... these symptoms alone will clog and kill a cat in no time, and I'm sure being of 20yrs old that possibly accelerated the process as well.

[scd88ga]

Depends on the quad fuel rail used too. Pauley's quad has a shrader valve right on the rail, Patrick's doesn't. Go figure.

88-90 Quad 4's have the earlier style with the built in valve, and 91+ are like the picture Steph posted.

[BadBerettaZ26]

Definitely no schrader valve on mine... I haven't even looked at the car today, I work nights and sleep a lot through the day. My weekend starts at 3:30AM tonight so I plan to go at it tomorrow. Gonna take it to get the codes read, and depending on the outcome of that, I might get him to check the FP at least. I have a DMM and Haynes manual so I should be able to check the other sensors, coils, etc myself. Also gonna check out the ECM to see if there is any corrosion or other problems there. If I can't track it down this weekend, I'm gonna break down and take it to someone and say 'just fix it'.

It's been starting a little better after running now, but that's about the only change. Still works bad and is burning almost as much fuel as my 360 Ram! Thanks for all your help guys, I'm still open to ANY suggestions you have!

[BadBerettaZ26]

Well after not touching the car all weekend, I finally got a chance to go get the codes read today. It had the following codes stored (Key on, before starting):

13 O2 sensor circuit open or no activity
15 Engine coolant temp sensor error (low temp indicated)
44 Oxygen sensor error (lean condition indicated)
55 ECM error, OR Digital EGR Valve solenoid 3 error

After starting it and allowing it to run for a minute til the CEL came on, it gave us the code 15 again. Scanner was showing -40* F for the coolant temp the whole time. Looks like it needs a new temp sensor! Makes sense to me, the ecm thinks the motor is retardedly cold and so is dumping fuel in it to compensate... I imagine the code 13 is due to me unplugging the O2 and running it like that for a short time, and not really sure about the lean condition 44, if anything it shoulda been reading rich, but if the temp sensor is way off I assume that would make it run in open loop anyways... That code 55 scared me a little, thinking the ecm was on the fritz, but it also shows that code for the EGR so who knows? I'm gonna put a new sensor on it and see if that fixes it. I'll probably pick one up on my way to work today and change it in the morning. I'll let yas know how it works out.

[3X00-Modified]

Whenever an O2 goes bad or is not present it throws a lean code and requests more fuel, its a safety deal also Lean is low voltage on the O2 circuit, so in order for it to read rich it would have to have a completed circuit registering over 1mV and you had it disconnected aka 0mV lean.

As long as those codes weren't present and just stored when running then you should be good replacing the temp sensor. And yes your thinking on that is spot on... And THAT is what caused your cat to clog... it's been dumping fuel thinking the temp was -40 and overloaded the cat with unburnt fuel therefore later clogging it.

Just clear the rest of the codes and see if the 55 comes back. The Digital EGR's are known to be a bitch and not work quite well.

[SuzukiGhostRider]

I will agree you need to change your CTS. It does have an impact on fuel air mixture and will cause rough idle and hard starts.

As far as the Cat while I'll concur it definitely wasn't a plus for the condition of it to have unburned fuel dumped into it, I still think age and who knows WHAT problems over the years caused it to finally collapse upon itself. The latest problem may have just been the last straw for an already weak Cat. The pic I showed you of one of my cars had ZERO other issues. It ran PERFECT until the Cat collapsed from age. It's not always a "cause and effect" type of thing, unless you consider age and time leading to destruction to be the cause and effect.

[BadBerettaZ26]

Well actually my cat was surprisingly UNclogged as well... It was nice and open through the honeycomb with only very minor residue/carbon/whatever on the front face of it... It just decided it was time to come apart, whether age or the current problems (or both) were the culprit.

For SOME reason, it worked great both going to, and coming home from work tonight. It only gave me a liiiittle bit of stumbling when I stopped for gas after work but it came right out of it. Fuel comsumption seemed much better too. Guess it knows I'm gonna fix it later today

[scd88ga]

While you're under the hood, also take a few minutes to examine those POS black nylon vacuum lines the run along the driver side shock tower to behind the battery and down front of the transmission for cracks, burns, rub marks, etc.! Just the slightest crack/leak can wreak all kinds of annoying havoc on how the car runs! Of course if your cruise control works and your interior air vents/doors open and close properly, then it should be of no concern because that means vacuum is good! This is just a little thing I have ran into on multiple occasions with various GM's that is very easily missed! Good luck, and I hope your Quad Z26 is happy again very soon!

[3X00-Modified]

Well actually my cat was surprisingly UNclogged as well...

Your contradicting yourself here...

It was plugged solid right at the outlet, I couldn't dislodge it with my fingers. So I got my trusty ol jackhandle and beat the crap out of it, start and rev, beat more crap out, start and rev again.... I got it all broke up and blown out, but the honeycomb must be in 2 halves inside the cat, front and rear if you will. I can see that there is still half of it in there but it is a nice perfectly flat surface that looks to be a complete full half. I left it like that for now at least, so I still have some cat efficiency there. I have to get a new piece of pipe for behind it so I may knock the rest out then.

If you cut open the cat and it looks like it did in those pics then you overheated it with the unburnt fuel (Just ask Geoff what color a cat turns when you dump raw fuel into it, He remembers from before he went OBDII) and with that over heating happening you cracked the material and it broke up causing your issue. This is a direct cause and effect deal.

Kinda sums it up right here.

Variables

The exterior shell is only one of the variables involved in the lifespan of a converter. A vehicle that rarely sees adverse weather conditions, where sand and salt are applied to the surfaces of roads, will last much longer than one that experiences them frequently. However, the exterior shell of a converter has nothing to do with how it functions. The internal component of the catalytic converter can be compromised by a poorly performing engine or a faulty oxygen sensor. Air and fuel need to be mixed properly together for a combustible engine to emit pollutants. Oxygen sensors monitor this even mix. If the fuel gets too rich or too lean, more pollutants will be released into the atmosphere, and the catalytic converter can be compromised by being exposed to the wrong temperature or buildup of carbon. When the oxygen sensor fails, it also fails to communicate correctly with the engine's computer. The engine makes adjustments to allow the vehicle to run under any condition, and either too much fuel or too much oxygen is then exposed to the catalyst. Too much fuel creates more unsupervised heat in the exhaust, melting the internal catalyst. Too much unsupervised oxygen allows potential pollutant particles to not burn properly and then adhere to the catalyst, thereby clogging it. A smooth-running engine which has had stringent maintenance repairs for tuneups, fuel injection cleanings and oxygen sensor replacements, will contribute to the longevity of the internal catalyst.