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Discussion Starter · #1 ·
I think I will start over again

I have an '87 SAAB 900T 16V Automatic.

Things that have been done or replaced: Rebuilt distributor / hall sensor, NGK plugs, Bosch cap and rotor, Bougicord wires, NTC, Bosch ignition coil, Bosch Throttle Position Sensor, new fuel filter, K&N air filter, turbo bypass valve. Bosch AIC, new vacuum hoses and cleaned the Mass Air Meter and every electrical plug and connection. I have also checked intake and inner cooler hoses etc..

The car starts fine. Most of the time it idles fine. No stalling. However, I drive to work (12 hwy miles.) Driving 65mph and around 3000+ rpms. Then out of nowhere the rpm/tach needle dives to zero and back up to 3000 - 4000 rpms maybe once or twice. This may occur around 4 miles into the drive. Car seems to drive normal again.
Then a couple of miles later the rpms will dip again.
Then closer to my 9 to 10 mile mark of my drive the tach bounces more frequent and the car bucks and hesitates and has many many times stalled at this point. The car will restart but almost seems like it is flooded. Sometimes after the second or third restart it will either restart and have an hunting idle or I have to wait 30 to to hour for the car to restart. Then I can restart the car and drive it to work and the cars symptoms will reappear.

I want to say this starts at operation temps. but sometimes that is not always the case. Sometimes (at night) I can drive it the same distance and not experience any symptoms. Perfect idle, no erratic rpms and no stalling or dying.

I have checked the Fuel Pressure Regulator for leaking (removing the vacuum line and looking for fuel and turning on the car to see if any fuel is present) but it seems to be fine.
 

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I know you have said the the distributor is rebuilt, but I would be looking initially at the hall sensor, it's wiring, plug, connector and wiring to it. Check it again.
 

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WIth the tach dropping to zero (or near there) it tells me you are looesing the primary side of the ign. So that is where you need to look. It also sound like it is temp related (happens more when things get up to operating temp.
Coil could be heating up and have an open or short to ground when hot.
a relay could be heating up and dropping a connection.
Hall effect pick-up is the most likely but not the only thing. There is the ign amplifier and the tach itself which could short to ground killing the ign signal. All of the wiring needs to be inspected for chafeing and breaks.
Intermittant electrical problems are the hardest to solve because you need to do all the diagnois when the probem is happening.
You can throw parts at it a hope to get lucky, or you can carry a voltmeter (or even a test light) and start chaseing the fault when it happens.
At least it is narrowed to one circuit, the ign circuit.
 

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Agree.....sounds like the distributor connector and wiring.......likely to be cooked from long term heat exposure - insulation and plastic crumbling.
Check for distorted relay socket and or cooked Ignition Relay (green Cartier relay) in the fuse box.
This occurred in the 86 I used to own, also there was a 4 pin relay style Ignition Signal buffer driver amp in the fuse box.
For a while I used this part as a security measure......if that relay/driver was taken out, the car died.
 

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Can better explain what you mean by bucking and hesitation?

Are you describing fuel starvation symptoms? Almost like an intermittent fuel cut? Is the bucking violent enough to require a firm grip on the steering wheel to avoid smashing your face into it?
 

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Can better explain what you mean by bucking and hesitation?

Are describing fuel starvation symptoms? Almost like an intermittent fuel cut? Is the bucking violent enough to require a firm grip on the steering wheel to avoid smashing your face into it?
If the tach is falling to zero, it isn't fuel related as the orignating cause. No spark= no fuel with this system.
 

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Why not? If its an intermittent fuel cut/stall why wouldn't the rpm's/tach drop?
because lack of fuel wouldn't cause an instanious drop to zero in engine rpm, the car, and its inertia will keep the engine turning at about the same rpm, slowly looseing rpm. An instantanious drop indicates a loss of tach signal which is also spark signal.
In otherwords it is an electical loss and not a mechanical or fuel loss.
 

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because lack of fuel wouldn't cause an instanious drop to zero in engine rpm, the car, and its inertia will keep the engine turning at about the same rpm, slowly looseing rpm. An instantanious drop indicates a loss of tach signal which is also spark signal.
In otherwords it is an electical loss and not a mechanical or fuel loss.
The loss of fuel can certainly be caused by an electrical issue. The fuel pump is electrically driven is it not? I would like to understand the OP means by bucking and hesitation first before jumping to any conclusions.
 

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The loss of fuel can certainly be caused by an electrical issue. The fuel pump is electrically driven is it not? I would like to understand the OP means by bucking and hesitation first before jumping to any conclusions.
Your missing the whole point. The indication is a loss of electrical feed to ignition primary, which yes, could also cause a loss to the fuel pump and computer feeding the injectors, BUT with the loss to the ign primary, you have a good starting point on the diagnoises. Solve the loss of primary feed 1st before anything else, if anything else.
I could be something upstream of the coil or dist itself, but is effecting them , like the ign relay, or ign switch which would also effect the fuel pump and injection, but if you start looking a fuel pump pressure and delivery, those things aren't the cause but an effect of the primary cause which is the loss of ign primary.
By useing the tach as a primary ign indicator, you have a big head start on finding the cause of problem. Solve the dropping tach, and you most likely have solved the whole problem. Without a tach signal the ECM will not deliver fuel. Ignoring the tach issue leaves a whole lot more to check, fuel being among them. Why make your life harder?
IF the orignal poster said the tach stayed with engine RPM but the engine lost power, then the field is wide open, and fuel would be one of the thing to check.
By noticeing the tach loss, he has cut the possibilitys greatly.
When turning wrenches for a liveing time is money, anything that can eliminate some thing or some system from the diagnoisis is a god-send, esp with electrical, and even more so when the problem is intermittant, like this one is.
I am not saying it is the coil or hall effect, although these may be the problem, but it is in the primay ign circuit which includes all the feeds to those parts.
The tach is just a "window" into the ign circuit that can be seen from the driver seat. This is not "Jumping to concluseions" but sound diagnoistic procedure based on the posters observations.

To put it another way, a loss of ign feed can cause a loss of fuel, but a loss of fuel will not cause a loss of ign feed, so if you look at fuel 1st you've add a whole lot more to look at that can not cause the problem as decribed.
 

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Discussion Starter · #11 ·
I have decided to take it to the shop. I really need my car. I'm tired of guessing and throwing money into it. My thinking is leaning towards the crankshaft sensor but Ill leave that up to the pros.

I do have a question about the crank shaft sensor. It is located behind the pulley but, where does the wire come out and connect to the the other connector? How much are they I have seem them at one place ( saab dealer) for $240.00.
 

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If this
I have an '87 SAAB 900T 16V Automatic.
.....is correct (???)
The car will not have any sensor behind the crank pulley.
All the ignition and associated signals stem from the distributor........

Crank mounted sensor for ignition signal is from MY89 on......and is only for non-turbo cars.
 

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Repeat, this is not a fuel issue. It is related to ignition. Hall sensor, coil, ignition amp, and possibly one or two other things connected to the ign. system. Don't let the shop charge you for anything else.

PS As Rodent says, your car does not have a crank position sensor. It is a turbo and has the sensor in the distributor. Double check the plug and wires on the distributor before you start spending money needlessly.
 

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it would take you 45 mins tops to test the ignition components yourself. I have done it a few times and got it down to about 20 lol.

The shop may charge you a couple of hundred for some piece of cake trouble shooting.

Here I'll write out the instructions for you - for completeness sake heres the lot (NB HES = hall effect sensor on distributor)

check power to coil (pins marked on coil)
- terminal 15 and ground (use coil ground then known ground - if there is a difference can be wiring fault)
10v+ with ignition on

test your ignition coil resistances (remove + and - wires )
pin 1 and 15 - 0.5-0.9 ohms
pin 1 and center tower 7200-8200 ohms

LEADS
coil HT lead - 500-1500 ohms
HT leads 3500-4500ohms

TEST at the hall effect sensor plug :
- 10v at pin marked + with ign on (use plug ground and known ground)
- earth at - pin (THIS COULD BE YOUR PROBLEM! if your dizzy is rebuilt, you can have bad 12v or bad earth causing you to temporarily lose ignition signal which would give tacho flop and bad jerking- wriggle the wires around whilst doing the test or get someone else to, do it for both 12v and earth wires.)

Test your ign amp (coil wires obviously connected but HES disconnected from distributor )
- measure across terminals 1 and 15 from coil and turn ign on, should read 5v that drops to 0 after a couple of seconds - if it doesnt ign amp is faulty

checking ign amp
-pull plug and connect meter to terminal 4 (+) and terminal 2(-) turn ignition on and look for 10 v

checking hall sensor output to ign amp (THIS IS ALSO A POSSIBILITY)
- peel back rubber boot on ign amp connector (leave connected) and connect volt meter between 6 and 3 and turn engine over by hand (spanner on crank or whatever) voltage should oscillate to 0.4v or less and 3v and higher (square wave) Wiggle the wires whilst doing this to see if you have wiring fault from HES to ign amplifer plug or faulty HES!



This took me 5 mins to write come on give it a shot!
 

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I don't if you have looked into these but it could be so simple as the ignition switch (in centre console)? and then next in line to that...the Ignition system power relay....(in the fuse box), burnt out relay sockets in the fuse box?
 

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Discussion Starter · #16 ·
Bad distributor was the problem. New mechanic was puzzled with what was going on. He replaced the distributor with one he had on hand and it worked like a charm.
Shouldn't my other mechanic have caught this while rebuilding the old one? I took it to the new mechanic because my old one was busy and backed up and had Techs on vacation.
Wonder what compensation I ask for? I'm sure I have found a new mechanic even though he is farther away.

Thanks guys for all your input.
 

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If you'd done the tests I listed you could have saved yourself some money.

Ah well glad you sorted it out.

The mechanic should refund the cost of the distributor that was 'rebuilt' and the costs for labour of installing it. The diagnosis probably won't be covered.

I don't normally condone it but if the mechanic refuses to be good about it threaten to put an ad up on craigslist defaming them.
 

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The mechanic should refund the cost of the distributor that was 'rebuilt' and the costs for labour of installing it. The diagnosis probably won't be covered.
In my book rebuilding a dizzy includes a new hall sensor. Wonder what he did apart from a wipe-over with an oily rag. :roll:
 

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probably wriggled it, then said he rebuilt it to get the extra $
 

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Discussion Starter · #20 ·
I replied back to his email and expressed my disappointment with the work and not being able to get me into his shop and requested a refund on his services. See where that gets me.
 
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