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Engine Management, Fuel, Spark, EGTs, and Air/Fuel Ratios This forum includes general electrical, modification, tuning, repair, replacement, identification and restoration of all components mentioned above including SMEC, SBEC, Logic Modules, aftermarket engine management, etc. Nitrous oxide posts go in here. This is the place

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Old 02-16-2013, 02:32 AM   #1
88 Omni, Running issues, Need some advice.  
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Hi there! Ok so I'm a newb and this going to be a long question. I got this car off Craig's list about two weeks ago. It's an 88 non-turbo omni 2.2L with a/t. I know the forum is for turbos, but in my googling, I ran across the two previous owners that I guess we're on here with it, so I figured I'd start here! :). - tried to post the link the to car from the other two guys, but no links as a newb. It's the grey 88' omni GLS clone in Daytona, fl from December 2012. I guess the guy I bought it from wanted to swap in a turbo but then sold it a month later. Not sure why the guy I bought it from sold it so quick... Hmm. Didn't see the car referenced here til after purchase.

Anyway, the car is pretty clean, and seemed like it would be a reliable daily driver to get me out of my 14mpg jeep while paying almost $4/gal. I used to have an 86 horizon, I loved that car- so when I saw this for sale and in such super condition, yeah- I wanted it.

So- when I first got it, it had a rough idle and a stalling issue where if you took your foot of the gas when coasting to a stop, it's like it would bottom out rather than drop down to the 900+/- rpm it should, and stall. It would start right back up again though. So I figured, the car was reasonably priced, throw some cash at tracking that down, I'd have a good little car for around town. I still don't think it's a big issue- but I'm having trouble figuring out where to look.

First thing, I took it to a shop to get it all gone through as I didn't have time that week to mess with it. I must say, all the shops around here are bupkis when it comes to this car. Three different shops had it two days each, they didn't do anything but mess with the plug wires and clean the throttle body. Did you check the timing? No. Uh, sensors, vacuum? It sounded ok... Seriously, it's a complete joke. I got mad at the last shop for saying they fixed it with new plug wires it didn't need and they said- well how good do you expect an old car like that to run? So it seems, that because I'm female and the car is an omni- I can't get anyone to give it a serious check and am now on my own. Plus, the last place it got it from, did the plug wires without asking me, I now also have a stumble at idle in drive.

So- onto the issues. Currently, I have a rough idle while in gear, tach reads 850-900- not apparent in N or park. Have an intermittent stumble when in gear at idle where it will quickly drop 100-200rpm and pop back up. Sometimes it won't do it for a while other times its 5-6 times/min, still others it will do it once or twice then not. Not sure if its there at speed, if it is, its hardly noticeable. But I do get what feels like a kick down around 40mph/1900rpm- not sure if its just the trans at a shift point or related to this. Exhaust smells like its running rich. It stalls on idle return, like if you blip the gas real quick, or instances like accelerating on a u-turn then off the gas finishing the turn, or pulling into my driveway where I'll be accelerating then off the gas to pull in. Sometimes it doesn't stall and just bogs and catches itself.

I put yet another set of plug wires in to eliminate the possibly that that shop put in a bum set. Did the basic: cap, rotor, plugs, coil, checked for vacuum leaks best I could, new coolant temp sensor, pcv, air filter. Have an idle air valve and tps to put in tomorrow, gonna try to clean the egr. Car was running cold and discovered the thermostat is MIA. Also found that the rad. has a small visible leak, and so slight bubbling at the rad fluid. Had one shop let me use their temp gun and it was 190 degrees about warmed up, so no over heating. I really don't think it's the head gasket, but I have heard they are a common problem on these. No smoke, no water in oil, cylinder compression *should* have been checked according to shop #2 who said it was good (but I don't know if I trust them on that). Also not sure, but might being hearing a water pump bearing going. Lastly, my oil pressure when driving warmed up is 1.5 marks down from the large line on the gauge (not sure the range on the gauge?), it comes down to the middle at idle. Oil level is fine- but pressure seems high?

So, I'm not sure where else to start looking for those issues

Beyond that, it starts right up, doesn't seem to have any power loss other than the fact it's an inherently slow car, all the goodies work and I only found a couple eraser size rust spots that I'm fixing with rust bullet.

I HAVE NOT checked the timing because, well- I'm learning as I'm going and I'm not sure where the timing window is to point the light at! Haha.. So, as an aside, if someone could give me a quick timing check rundown and location for timing check? ::grin:: I haven't had a timing light out for over 12 years. I did briefly check that the belt is running toward the inside very slightly and has more slack in the front than the back.

Ok, sorry that was long! Thank you so much for any help!
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Old 02-16-2013, 02:42 AM   #2
Re: 88 Omni, Running issues, Need some advice.  
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Oh! And I forgot to mention: it isn't throwing any codes via the ignition method (I do this on my jeep too).
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Old 02-16-2013, 05:33 AM   #3
Re: 88 Omni, Running issues, Need some advice.  
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Welcome To TD!!!

What is engine vacuum reading at a manifold source at idle?
Are the plugs showing any signs of fouling?

One of the common problems on the low pressure TBI was the injector.
The injector is a ball and spring design and the issue was that when closed the spring would not hold the ball down and it would bounce creating an extra shot of fuel causing a rich running driveabilty condition.
You can view the injector spray using a timing light.
Connect you timing light as you normally would only shine the light on the injector and watch the spray.
The spray should be in a conical shape with atomized fuel with no large or extra droplets.
If you see larger droplets replace the injector.
Using a timing light with an advance meter will allow you to sync the light with the injector.
Cleaning the injector will not help since the ball and spring design do not get dirty...
"A rolling stone gathers no moss"
Even if you find a faulty injector you may have other issues that have to be attended to.

Here is help on checking Cam and Ignition Timing.

CHECKING CAM TIMING
http://www.turbododge.com/forums/f4/...n-84-95-a.html

CHECKING IGNITION TIMING
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Old 02-16-2013, 07:43 AM   #4
Re: 88 Omni, Running issues, Need some advice.  
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Welcome to TD :)

intermittent drivability issues can be tough to track down,
but persevere! a properly running TBI omni is a wonderful thing :)

based on careful reading of yur post, I suggest:

1. the random nature of this suggests electrical, Primary Ignition ..
our TDs use a "Hall Effect Pickup" HEP in the distributor to send trigger to the computer ECM for ignition timing..
these are Notorious for intermittent failure, either
1. wire leads to HEP get pinched under dist. cap and short against dist. body;
2. as HEP gets old, random drop-outs occur, often becoming more frequent until total failure
(this is often more apparent when weather/car is hot)

"Real TDers" scavenge these off junkyard cars, and carry a 'known good' spare in the glove box, with a phillips screwdriver ;)

2. doublechecking vacuum lines and replace ANY suspect lines or elbows, tees..
or simply replace them all with new lines.. its pretty cheap to do, just takes some time

our old TDs are notorious for having brittle, cracked plastic and dried out, cracked rubber vacuum lines with variable/transient vacuum leaks..
perhaps changing as engine moves, or components warm up..
can be Frustrating!..
Plus, our FI computer relies on having a SOLID vacuum signal to the MAP sensor and FPR..
disruption (transient leak) here will result in radically wrong fuel injector pulse rates.,.
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Old 02-16-2013, 09:25 PM   #5
Re: 88 Omni, Running issues, Need some advice.  
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Thank you!

Ok, haven't hooked a proper gauge up to it- I had tried using carb cleaner :) will report back on that tomorrow. Put the new IAC sensor in today, seemed to run a little better but still getting that blip in idle- but only in drive. What did happen though was, when in park, if hitting the gas only very slightly it would take off and go up to 2500rpm for a few seconds then back down. Is that a sign of vacuum leak or something else?

I've had a couple few people mention several issues involving the distributed as possible culprits- should I just replace it?

As for the plugs- no a but of carbon, nothing horrible, I'm assuming since it smell rich the carbon could be from that?

Ok- thank you! That timing procedure makes way more sence than the Hanes version. One tiny stupid question though- where am I looking for the timing marks? It says on the transaxle? I'm just not seeing anything.... The picture in the Hanes manual gives no hint, haha

Didn't get the tps in today- someone cranked those screws in there, I found lock tight on the IAC, so I'm guessing they used it on the tps too. Gonna try when it's warmer and brighter tomorrow, they are wanting to round out.

Oh! One more thing- I tried to do the lift gate struts today, the ones the shop sold me won't hold the lift gate up, and the correct listed part for this car isn't a match. They one they list has loops on the ends and the one that's on there has the ball socket type... Any ideas what I'm looking for to get a hatch that will stay open? Also the intermittent wipers if I switch them up to high speed and back down, stop being intermittent and just stay fast until I turn them off for a while.... Does this require a new switch or can I fix it?

Thank you so much for all the help!
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Old 02-16-2013, 09:38 PM   #6
Re: 88 Omni, Running issues, Need some advice.  
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Wait! I have one more silly question! My fuel gauge is pretty regularly telling me I have less gas than I do, but it does move around with refueling and driving. I'm assuming this is the fuel sending? Or the float? Any way to fix it? Right now it's saying I've used up a quarter tank on 18 miles, my be running bad, but not that bad- no fuel leaks that I can find.
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Old 02-17-2013, 02:05 AM   #7
Re: 88 Omni, Running issues, Need some advice.  
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Ok- here's a question, after reading on allpar for a bit, it sounds like my problem could be a combination of the speed distance sensor and the Hall effect in the distributor... Plus maybe a vac leak (which I might just start replacing vac lines like was suggested). Does this sound right? Where is the speed distance sensor located?

Also- when I was doing the idle air valve, I had to remove a sensor to the right of it to get to the screws. It had white something or other all over the tip that goes in the TB- what is that, what does it do and what it the purpose of the white stuff?

Haha, sorry- bombarding you guys with questions.
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Old 02-17-2013, 03:32 AM   #8
Re: 88 Omni, Running issues, Need some advice.  
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timeing marks are on the bellhouseing of the transmission directly below the end of the cylinder head - there is a rectangular hole there so you can see the rotateing mark on the flywheel inside the bellhouseing

if your going to make a timeing adjustment , there is a sensor to the right of the thermostat houseing - unplug that first

this is done so the computer dosent't think the change in timeing while adjusting it is a fault

once adjusted plug it back in
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Old 02-17-2013, 05:56 AM   #9
Re: 88 Omni, Running issues, Need some advice.  
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Seems lke you are reading too much and getting to the point you want to replace everything...Not good.

The factory used loctite on the TPS and AIS screws.
Use a micro-torch to heat the area where the screws go in on the throttle body to loosen the loctite and remove the screws.

There is a pic I drew of timing marker in the timing belt link I posted.
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Old 02-17-2013, 03:53 PM   #10
Re: 88 Omni, Running issues, Need some advice.  
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Ok! Got the timing checked, it was at around 10 instead of 12, I moved it to 12 and now I'm having what sounds like a miss out of the exhaust in park? It's idling in drive better, but still has that stumble. Also, when the coolant temp sensor was unplugged, it was loping in idle until I turned it off and plugged it back in- is that normal? - got the tps in too...

:) I don't WANT to replace everything, I'm just getting frustrated not being able to figure this out, and ofcourse worrying about driving it until then. I'm just learning what does what here...
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Old 02-18-2013, 08:06 AM   #11
Re: 88 Omni, Running issues, Need some advice.  
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With the CTS unplugged the car is in "failure" or " limp in" mode and will not run correctly.
Disconnecting the CTS with the engine running puts the car in failure and the engine controller stops spark advance and timing goes to "base" where you are able to check and set.

1)Are any of the plugs showing any signs of fouling?
2)Have you looked at the injector spray pattern as I previously posted?
3)Did you verify Cam timing was correct?
4)What is engine vacuum reading at idle?
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Old 02-18-2013, 02:21 PM   #12
Re: 88 Omni, Running issues, Need some advice.  
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Ok- like I said- learning as I go! Sorry! I do not own a vacuum gauge, will have to buy one later in the week- where do you want to take a reading from? And what *should* it be?

I have to admit, I'm a bit daunted by how to verify the cam timing- yes, I read your instructions- how do I rotate the crankshaft by hand? And how do I know I'm at TDC on #1, by the position of the rotor? I can say the belt is riding to the inside slightly, so it must be a bit loose? - sorry, never had to do it before.

Yes, I did check the injector- it isn't a FINE mist, but rather uniform small droplets- not entirely sure what it should look like, but the fact that it isn't a mist is a sign of a faulty injector?

Like I said- the plugs showed signs of it running a bit rich, but nothing else - ill check these new ones again now that it's been idling and driving around the neighbor hood a bit.
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Old 02-18-2013, 03:57 PM   #13
Re: 88 Omni, Running issues, Need some advice.  
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a mist is what you want. sometimes these cars were driven very softly, especially automatics. the engine like to carbon up.

try a can of decarbon down the engine while running. follow the directions on the can. then beat the shit out of the engine, run it hard on a roadtest, right to redline. you may need to replace the plugs after, the decarb chemicals tend to eat them.

carburated engine get this alot, and i've seen it on TBI motors too.
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Old 02-19-2013, 09:43 AM   #14
Re: 88 Omni, Running issues, Need some advice.  
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Do not be afraid to ask any questions, questions are how we learn.
If there is something you do not understand I will try my best to clarify.

Engine vacuum needs to be between 16-20 " HG(inches of mercury)at idle measured at a manifold source.(port coming directly from the intake manifold)

Vacuum also needs to be measured at the Map Sensor.
The Map Sensor is the dominant fuel control sensor.
If engine vacuum drops the engine controller see's this thru Map sensor voltage as more air entering the engine so it adds more fuel.
If vacuum is low due to a vacuum leak or engine mechanical problem adding more fuel causes a rich(too much fuel)running condition.

When you check vacuum you will want to "tee" into the vacuum line with the gauge.
Disconnect the line from its source, insert a plastic vacuum tee and use 2 more pieces of vacuum hose to reconnect to the component and connect the gauge.

When checking cam timing, remove all 4 spark plugs,it is easier to turn the engine by hand.
Mark the ignition wires so they go back to the cylinder they were removed from.
You will want to install a socket on the crankshaft pulley bolt and use a ratchet or breaker bar to turn the crankshaft(clockwise).
The piston will be at TDC twice, you want to be on a compression stroke(dist rotor pointing towards #1 cylinder on the cap and the oval slot on the cam sprocket towards the top)
When the piston is at true TDC the mark on the bellhousing(where you checked ignition timing)will be aligned with 0.

Without seeing the injector spray it is almost impossible for me to say either way.

USING A VACUUM GAUGE
How to Use and Interpret a Vacuum Gauge

CHECKING THE MAP SENSOR
http://www.turbododge.com/forums/f4/...agnostics.html


MAP SENSOR PRINCIPAL AND THEROY OF OPERATION






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Old 02-20-2013, 09:43 AM   #15
Re: 88 Omni, Running issues, Need some advice.  
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Have you checked the O2 sensor? These usually fail in the lean state and could cause your rich condition.
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