RandyNJ

The car sat for nearly 3 years, but ran fine before sitting. Was not running at all and running rough if I luckily happen to get it started while trying. Car has currently been in a shop for nearly 4 months. First I was told it was the fuel pump, they replaced that. Next I was told the egr valve was stuck wide open they replaced that. Now I'm told that the car runs everytime, but runs rough. The shop said if they take the MAP sensor out the car runs rough, but with the MAP sensor in it doesn't start. They told me they're checking wires that it's something electrical. Is there anything that specifically has these "symptoms"? A new MAP sensor was already put in.

Tuned Performance

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southbay08

Thanks Tuned Performance....
There's a good chance that the injectors could be clogged.

Tuned Performance

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tealman92

When these cars stit the fuel eats the fuel pressure regulator diaphragm. I would replace the Fuel pressure regulator and injectors.

ULTM8Z

If the map sensor is removed, the ECM "sees" atmospheric pressure in the intake manifold and will increase the fuel delivery during open loop operation thinking you have a high-load condition.

So if something is causing a lean condition during normal fueling (i.e., clogged injectors or something like that)... so much so that you can't even start the car... then having the ECM artificially increase the pulsewidth of the injectors for the above reason may be enough to overcome that lean condition and get it to start, but still lean enough to cause a running issue.

Though I'm not sure about the clogged injectors scenario... maybe a couple are clogged, but all of them? Preventing the car from starting at all? I do agree though it would probably be prudent to replace them as they're now going on near 30 years old if they're the originals.

There's also the possibility... maybe a problem with the fuel pressure regulator, such that if it's leaking, you may not building enough fuel pressure to drive the injectors properly.

Have they checked the fuel pressure by priming hte system (key on, engine off) and watching the pressure? It should hold pressure for a long time without decreasing.

GeneralDisorder

iTrader: (1)

Injectors are shot, and the shop it's at isn't equipped to work on this type of car (and probably a whole lot of other cars that don't say "Hot Wheels" on the bottom).

4 months is about 3 months, 30 days, and 22 hours over the time required to perform the diagnostics this problem requires.

I have seen 3 injectors stop working after sitting for a couple years. Barely able to start on 5 out of 8.

They are troubleshooting by Visa - and it's YOUR Visa. This is NOT a shop capable of proper diagnostics. Either they lack the skills or the equipment or both. PERIOD. You need to remove your car from their "care" IMMEDIATELY.

GD

scooter

iTrader: (11)

Where in NJ are you?

JoshHefnerX

If the car has been sitting there for years before you got it, you probably should go through the entire fuel system anyhow. Fuel injection is better than carbs about gumming up but they're not infallible. New pump, fuel filter, regulator, and injectors should have been assumed. Sensors can generally be tested, via volt/ohm meter, and they could have all been checked easily. If all that checks out it should run, unless rodents were eating the wires...

Pro

Do an injector balance test. There are videos all over youtube how to do it with a tool from amazon or ebay for like 15 bucks and it's so quick and easy. It basically does the same thing that newer ECMs already have built in that professional scanners can access and use.
I found 2 out of 8 bad injectors. 1 on passenger side bank causing lean, and 1 on drivers side causing rich. But since the O2 is on the drivers side, the computer thought the whole motor was running rich. So when it started to take fuel away due to the rich, passenger side became even leaner. I bought 8 new ones from southbay and now the car runs perfect (and didn't need to mess with fuel tables like most people need to for some reason).

Turbo Lover

I am having the exact same issue on my 1987 305 TPI. Car sat for 2 years and then wouldn't start. Sat for another 2 years until now when I have had time to work on it. Installed a new fuel pump/sending unit and fuel pump. Starts but runs really rough. I checked the resistance of the injectors and they metered ok. I doubt that tells me how well they are flowing though. I will look up the balance test. So glad forums like this exist.

Thanks everyone for your input.

GeneralDisorder

iTrader: (1)

All the injectors that sat in my 86 Trans Am ohmed fine after 11 years sitting in the woods. Not a single one of them would even open when applying a 9v battery. Zero fuel flowed through them, and I do mean ZERO. So the ohm test really means nothing in terms of their actual operation. What's easier than the balance test is to just listen to them with a stethoscope. It's pretty easy to pick out the stragglers.

RandyNJ

Could something be causing the map sensor to send incorrect or no voltage to the injectors? That's what it seems like is happening, but I was told they already tried a new map sensor.

Tuned Performance

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GeneralDisorder

iTrader: (1)

LOL. We already told you what is wrong. It needs injectors.

GD

RandyNJ

Injectors tried already. Was told it's an electrical issue. Also was told it's a 91 that their scanner doesn't show codes, but it is showing a code for a sensor. The car starts with the MAP sensor out and runs rough. With it in it struggles to start. A new MAP sensor was already tried. It's also important to note when the fuel pump was replaced since that was suspected at first, 2 gallons of water came out of the tank

Tuned Performance

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RandyNJ

i'll mention this next time. The issue is I can't try the things you're suggesting since I don't have the car with me.

Tuned Performance

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Tuned Performance

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RandyNJ

Looking for information to suggest to the shop mainly since apparently they seem confused. Would work on it myself, but don't think I'm at that level yet and I don't have a garage or tools. These shops tell me they know how to work on the car

Tuned Performance

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GeneralDisorder

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+1

They would have solved it by now if they knew what they were doing. This is rudimentary MPFI diagnostics.

The map sensor (and intake air temp sensor) are most directly involved in fuel calculations. Unplugging it will result in the ECM running excessively rich. And you claim it STILL runs rough. This would suggest it's still lean (injectors).

They "tried" a new set of injectors? What about the fuel pressure regulator?

Do these idiots even have a wideband so they can see what is actually happening with the fuel mixture?

GD

scooter

iTrader: (11)

Where in NJ are you? I know a shop in PA that actually knows 3rd gens, is honest about stuff, and would get it fixed quick and not use your wallet to troubleshoot it.

vinny R

You should definitely pull the car from the shop it is at. It sounds like they just don't know these cars and are just throwing parts at it. GD and TP are some of the best on this board for solving issues on these cars. These cars are fickle when it comes to the computer systems and most times even if you have a code, something else is wrong causing that code.Your car sat for 4 years...the problem is most likely in your fuel system. If you look at the previous post your car won't start with the MAP. It does when removed. When you do this the computer compensates by delivering more fuel...and now it starts. IMHO your injectors are clogged from sitting for 4 years.

cardo0

You need to put some run time on that car. Not many owners realize that once the battery is disconnected or goes dead the ECM has to go through adaptive learning where the long term fuel trims are correcting from the stock base tune. I saw this on a C4 corvette I test drove with only 15K mi on it. The original owner couldn't figure it out since the batt was always disconnected when in storage and wan't to unload the car still in perfect condition. Kinda chugged on each start from a full stop. Had same thing only worse on a mail order tune for my 4th gen. That thing died on first start up with new tune and was scary to drive the first few miles. But after an hour it was fairly smooth cruise'n.

RandyNJ

I'd bring it to another shop, but there's none that I know of nearby. Seeing as I'd have to tow the car I'm also trying to stay local.

Not exactly sure if it matters or changes anything... the previous owner had a performance chip put in. I'll look into what you said

Tuned Performance

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GeneralDisorder

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He's not telling us what has been tried. I don't think he knows.

Honestly you would be better off bringing it home and letting us guide your diagnostics. Buy a few tools, learn to use them. Really this only requires a few things like a DMM, maybe a few fuel system testers. You can get cheap pressure gauges, and an injector tester that pulses the injector via a timer to check pressure drop.

4 months is long enough to have completely learned MPFI diagnostics and have your car running on your own. You really think these guys at this shop are smarter than you? You can poke at the engine bay with a stick just as well as these monkeys.

GD

vinny R

vinny R

If you don't want to pull the car from the shop and you tell them what to do, I think I would have the shop pull all the injectors and you can mail them to Southbay and they will not only check the OHMS part but the floe also.

RandyNJ

Had it at a different shop before this one and they told me they tried two "new" ecms in case the first one they got sent was bad. Plugs and wires were replaced (note this shop was dumb and didn't drain the tank) after the car sat for 3 years. They eventually told me they couldn't figure out the issue and told me to tow it away, so it ended up at the shop it's at now for months. This shop drained the tank and said they found nearly 2 gallons of water in the tank(no idea how this got there). They told me they know how to work on the car before I brought it there... Guess every shop will say that. This shop immediately said it's the fuel pump and replaced that along with the fuel rails. Next it was the egr valve which they claim was stuck wide open, saying that was definitely one of the problems wrong. Then from there we some how got to the car only running with the MAP sensor out, but running rough. I suggested injectors from the start and was told "I don't think it's that". They now 4 months later told me they tried injectors and it didn't change anything. Also... the shop has never called once to update me on anything, so I have to constantly call them to see what's going on You now have as much information as I have Oh and also just to give an idea how clueless these shops are... When they mentioned the ecm and I replied with "two ecms were already tried" I got the response "oh no one ever told me that". This was the first thing I told them when I brought the car there and they were putting all the information into their computer. Sometimes I think I can run a shop better than these shop owners.

GeneralDisorder

iTrader: (1)

As a shop owner, I can say we are not all this incompetent.

You don't "try this and try that" - you TEST this, and you TEST that, and then you verify the TEST with more tests if you can. THEN, and only THEN, do you replace a customer's BAD part with a good one (which often needs to be tested and compared to the old prior to installation). They are doing what us accomplished diagnosticians call "troubleshooting with Visa".

You don't TRY new injectors - you remove them, and you test them on an injector flow bench (yes I own one), or you send them out to BE tested at an injector shop. You don't TRY a new ECM - you rule out all other causes for a bad sensor reading, lack of input, lack of output, lack of communication, etc, etc, then you test all powers and grounds, then you double and triple check EVERYTHING again, tap on the ECM with a hammer, offer it a few drinks, call it's mother..... and if you still don't get any action then MAYBE after a long, hard stink about it - you order one up and 50% of the time you are still wrong. It's almost never the confuser that's at fault *in practice*. It does happen though - sadly.

This stuff is REALLY simple, and these guys, despite their claims, have NO CLUE what they are doing. They are poking around like Monkeys - unplugging things and seeing if it runs. Sure you can probably affect some change in the running conditions of the engine by causing it to fault out when you unplug critical engine sensors responsible for fueling calculations - but they don't understand the fundamental interaction of all these components and until someone comes along that does - this car will remain broken.

As to them claiming ignorance of the other shop having tried a couple "new" ECM's.... doesn't matter in the least. I take all that $hit - whatever the last shop said, whatever "diagnostics" the customer has done and I immediately wipe my a$$ with them and burn what's left. Means nothing because the last guy didn't fix the problem. So his experiences or opinions are useless to me.

Funny thing about this - the shop would actually make more billable hours AND have happier customers if they did the correct troubleshooting with proper explanations of WHY they did what they did (to save money on buying parts you don't need) than throwing a bunch of parts at the problem, telling the customer they had 18 component failures (no one believes this - even retarded customers) all at once and presenting a huge bill composed largely of parts they have massively inflated the prices on - customers are not as keen on this approach. They are much more understanding when they get a bill for 6 hours of diagnostics and a single part responsible with a HUGE explanation of every diagnostic step that led to that conclusion.

I'm not saying that throwing a part at a problem is *always* wrong - in some cases it's the only option..... I have examples if interested.... but for the most part it's wrong, it's wasteful, and that is NOT why we were hired in the first place. Any idiot can do that - they shouldn't be able to call themselves "mechanic" though. Not and expect to not be called out on it.

GD

southbay08

Did they actually install a different set of injectors? What kind of injectors did they "try"?
If a vehicle sits for 3 years without the fuel being drained...I can't imagine that injectors are still functioning properly
besides if they're the stock injectors I bet the coils are shot as well.

vinny R

I would Join AAA and have your car towed out of that shop. A basic Membership is cheaper than 1 tow and you will get 3. I think (know) you are getting the runaround and they really do not know how to fix your car.

RandyNJ

Is the dealer usually any different than a private shop when it comes to knowledge about the car or are they just going to throw parts at it too? When I called to talk to them they said they would immediately want to hook it up to diagnostics which is already a flat rate fee where as most private shops near me give "free estimates" however these private shops seem to not have the correct equipment to deal with the car. Two different shops complained about not being able to read the codes...

GeneralDisorder

iTrader: (1)

The dealer is not likely to have the required knowledge. They may have the equipment, but the old timers that have meaningful experience with these systems likely retired years ago. Dealers rarely see anything more than 10 years old. It's now been more than 15 years since the dealer regularly saw these cars. And a Master Tech with heavy diagnostic training and experience with these cars is likely to have moved on from the dealer level, entered management, or retired.

What you need is a shop that can and does do custom EFI tuning, has a chassis dyno, etc. Those are the guys that can do diagnostics on your issue.

GD

vinny R

I agree, I don't think a dealer can help on this. Also OBD1 is a old system that is not very sophisticated and even a code may not tell you your problem. It most always is just a starting point on what system to look at. My buddy's 92, we kept chasing an O2 code. O2 sensor was fine, as they usually are. After a day of checking the fuel system, we found it to have a bad TPS. The TPS was causing a rich condition that was triggering the O2 sensor. If you look @ the post from Southbay Injectors, I think those are your issue or at least a starting point.

RandyNJ

Injectors were replaced. Car starts, but as soon as the map sensor is put back on it starts running rough again. Any ideas?

GeneralDisorder

iTrader: (1)

What does the MAP sensor live data show? What are the BLM/INT readings with it plugged in?

GD

RandyNJ

Apparently I was mistaken. Car starts up and runs, but after idling for a few minutes it begins running shitty with the map sensor in. I guess you'd still need readings to know anything... which I don't have as I only know what the shop tells me. Plugs are also black, so maybe the bad idle is just caused by fouled plugs?

GeneralDisorder

iTrader: (1)

Sounds like it's rich. Need to know the BLM/INT, open/closed loop status, coolant temp sensor reading, etc. You could buy a live data scan tool and we could help you to diagnose this. But yeah without any data to interpret what the ECM is seeing - really nothing we can do through the internet.

Shot in the dark - bad coolant temp sensor. That's the exact same symptoms I've seen from them.

GD

Pro

Here's a cheapo
https://www.ebay.com/itm/12-Pin-ALDL...r/273066388728
It'll sync with your phone via bluetooth.

RandyNJ

Extremely funny you say this. There's a coolant leak according to them and they have the entire part of the hose cut with coolant shooting out if ran Didn't mention this since I didn't think it would be related.

ULTM8Z

running better with the map sensor out seems to suggest that it needs a lot of extra injector pulse width to compensate for some other issue.

GeneralDisorder

iTrader: (1)

I was just working on a TBI truck that would act similar when you unplugged the MAP. Turned out it was high fuel pressure (17) and running very rich. Unplugging the MAP must have leaned it out (at idle). Seems that GM's fueling scheme for MAP circuit failure will lean out the idle..... With his symptoms, my recent experience with that truck and other third gens that have sat..... 99% chance he needs a coolant temp sensor. Probably needed injectors but that's fixed now.

How can they run it up to operating temp to see how it behaves if it's spewing coolant? Damn these guys are total hacks. Bad CTS should take about 10 minutes to diagnose with a proper scan tool.

GD