Hey,
I have a 1991 300zx with a rough idle and sometimes it stalls out on me when i am in neutral for longer than usual. I took it to a shop called Sound Performance and they said that it was the injector harness. They replaced that it did nothing, so now the shop comes out of nowhere and says o wait it wasnt that it was the egr valve and it needs a whole new engine harnes which of course is the most expensive thing for them to do ($2300) because they said you have to pull the engine for both things.
Does anyone know how to pull the egr valve without pulling the engine or is there a way to bypass the egr?

1991 300zx
ingen intake, e prom upgrade, Stillen headers, Stillen upper and lower plenum, HSK Dli type ingition, and stage 3 clutch

 

engine has to be removed or slightly lifted out for access to egr valve.

 

Read up on 91zxtt's mod updates here:..... A Wealth of INFO

 

Since I have removed the engine in this car I can tell you that you can remove the EGR with the engine still in it; however, you need to hold the engine up with a cherry picker, drop the center support and slide the engine forward (tranny included). That will give you enough room between the engine and the firewall to remove the EGR valve. You can replace the EFI harness this way also.


EGR valve usually doesn't cause the car to die. High idle maybe, but not die.

What shop advised you to install the DLI ignition? It's a waste of $ on an N/A.

Try cleaning your throttle bodies and IACV. Replace your spark plugs. Try using sea foam.

Check the resistance on your injectors. Should measure approx 11 ohms.

I'm not going for the EGR or the main harness. It's something else.

 

The ignition system was on the car when i bought it. The idle doest run high it goes low it. Runs better when its cold then the idle starts to go down. The spark plugs were replaced with platnum plugs. Whats sea foam? All the injectors tested good on the computer its just the connectors would slip off the injectors and cause the car to misfire so the injector harness was replaced.
thanks

 

haha thats the first time ive heard that. you probably need to adjust your idle control valve then...i believe

what kind of plugs are they?

sea foam

 

I played around with the idle control valve on it and nothing just either to high of idle or way to low of idle and the car would still die, nothing in between. The plugs that i used are called Platnum plugs they ran about $15 a piece. This weekend I am going to try and do sea foam and clean out my t/b.

 

does it run extremely rich? can you smell a really heavy sulfuric (rotten eggs) smell while idling? thats typically the tell-taled sign that you've got a egr valve issue. it will cause a poor idle! hard start, poor performance etc. i'm not so sure that an egr valve will cause a high idle. I do know that it will cause the above mentioned symtoms. as for the seafoam. i'd hold off on that stuff too. what people dont realize is the fact that stuff produses pretty nasty exhuast. that can be pretty devastating to oxygen sensors, or catalytic converters. try the throttle bodies. as far as the harness problem is concerned. there should be small metal clips that prevent the conectors from slipping off. why would they tell you that you needed a harness for that reason only? surely you could obtain those clips from a nearby slavage yard. o and one more thing. i just replaced the fuel injectors in my 92 NA, before i used to have the same problem. you let it idle for about fifteen minutes after it's already up to operating temp and then it would surge, the idle would drop, eventually it fall on it's face. after i replaced the injectors i havent had a problem since then. it runs very smooth at all times.

 

and i forgot something. injecrtor resistance. 10-14 ohms. and yes the egr valve will cause the vehicle to die.

 

I've never been witness to that.

 

taken from TTZ tech pages
heres a write up on how to check your egr valve and replacement

http://www.ttzd.com/tech/engine/egr.html
is that hose reachable with the engine on tho?

 

on any egr valve, if you reach underneath it and push in on the rubber diaphragm, the vehicle will start and die, start and die, until you let go. you're essentially simulating and stuck closed egr.

 

well....it does

 

I stand corrected. I read up a bit on EGR functions. Google can be a good thing.

EGR Valves have been around for a long time. Way back in 1972 GM used them in an attempt to reduce emissions of oxides of nitrogen (NOx) which were a major cause of air pollution, mainly photochemical smog, that kind of smog which is formed when strong sunlight shines down on the exhaust gasses we puke out of our tailpipes by the billions of cubic feet a day.

A short chemistry lesson is in order here. It was discovered way back when, that high combustion chamber peak temperatures (the really short duration high temperatures near the end of the combustion process) caused oxygen and nitrogen to combine chemically and form these oxides of nitrogen mentioned above. Most of the anti-pollution devices of the day did a pretty good job of reducing the other bad by-products of combustion, namely excessive hydrocarbons and carbon monoxide, however they tended to induce the formation of oxides of nitrogen. Something had to be done else we would all die of smog diseases.

The automotive engineers figured that they needed to do something to lower the peak combustion temperatures which only occurred under certain high load driving conditions. They figured they could do so at the expense of power and fuel economy but what the heck, ya can't have everything! If they could only add something to the combustion chamber that would act like sort of a fire extinguisher to cool the combustion temperatures that would do it.

So they invented a way to allow some very inert gas to get back into the combustion chamber only when needed. They needed a source of this gas - it wasn't air, cuz that contains oxygen and nitrogen which caused the problem in the first place. So they chose carbon dioxide. Where to get a supply of carbon dioxide . . . ??? Hmmmm, how about the exhaust system? That is mainly carbon dioxide and water (plus a zillion other noxious chemicals) Suppose we allow some of the exhaust gas to get back into the intake manifold under strict control and only when we need it? That would cool the combustion chamber and prevent the formation of the NoX. Maybe we should call it recirculated exhaust gas (REG??). But a guy named Reginald voted no cuz he didn't want his name associated with a car part, so they called it exhaust gas recirculation (EGR) since there was nobody around with that name.

Now we understand why it is there. And we understand what it does. So what can go wrong with it and what are the symptoms??

It's really pretty simple - it can be open when it isn't supposed to be, or it can be closed when it is supposed to be open. Not rocket science, but it is science. If it is open when it is not supposed to be open, at idle for instance, It will act like one monster vacuum leak and the engine will not idle or will idle really roughly. If it doesn't open when it is supposed to open you will probably experience a symptom of "pinging" or "knocking" since the combustion chamber temperature will be higher than normal (one of the main causes of pinging in an engine).

There are a zillion different types of EGR valves some of which work strictly on vacuum, and some which work on a combination of vacuum and pressure. Some have electronic controls, some have mechanical controls. I won't go into detail here about all the different types but suffice it to say that most can be checked by looking inside to see if the plunger shaft is stuck open or doesn't move when the engine is revved up (after it is warmed up). Replacement is probably the easiest part since most are held in by two small bolts and have a vacuum line connected to it. The hard part is whipping out your Visa card to pay for it since most of them will drain your reserves in a hurry!!

 

thankyou for clarifying, that was a most informative editorial.

 

Before reading that, I had always wondered why people have had overheating problems in these cars after they remove the EGR valve. This explains it.