Hi, I've run out of ideas trying to fix this. Car will start fine, settle down within a few seconds and then almost die, then surge, then almost die. I can see the idle control moving the throttle. I've checked the MAP sensor and it seems to work (5v in, 5v out), I've looked for vacuum leaks, changed the fuel filter, and a few other things. No progress, some advice would be great as thus is a new car to me and I'm only used to working on much older cars with carburetors and no computers. I really want to learn and fix things but I've got stuck with this thing so far.

 

Unstable idle is, 99% of the time, a vacuum leak. It maybe be an internal leak..... Disable the PCV system, pull the oil cap off, and start the motor. Is it sucking in, or blowing out the oil fill hole?

 

Thank you for your reply. I just tried that. I clamped the PCV hose and put my hand over the oil filler and there was no sucking on my palm.
I found a video on youtube about checking the codes through the check engine light flashing. I got a 13

13**No change in MAP from start to run. No difference seen between the engine MAP reading and the barometric (atmospheric) pressure reading at startup. Indicates a problem with the MAP sensor vacuum system.

Maybe a new sensor is needed?

 

Where IS the map sensor on that engine? It might be as simple as the vacuum line going to the map has deteriorated, and cracked.

 

It's above the engine. The engine is set back and is really inside the van next to the driver, so there is a tunnel in the bulkhead and its held to the underside, drivers side, of that. The pipe goes from the throttle body towards the rear of the van, then via 2 right angles goes back towards the front over the rocker cover and up.

The pipe, when I put my finger over one end of it and sucked, held a vacuum and my tongue stuck to it. However the outside is a bit hardened. it seems to be in two parts with an inner liner. I question if that liner may have become separated from the outside and is collapsing in and stopping the vacuum pressure getting to the sensor. A long shot but given that it is old and brittle anyway, I've ordered a new one.

I do have a Haynes manual and I've been checking out the wiring. My MAP sensor has 3 wires. One is +in, one +out and I assume the other one is earth. The + in is pink(violet) and white and shortly before the MAP sensor is joins two other pink(violet) wires. They are all soldered together which doesn't look factory fit to me and I question why. Right now I am thinking that there used to be a connector there which got damaged (it kind of touches the throttle spring) and was repaired. The wiring diagram seems to suggest it is correct to have that 2 into 1 but I'd welcome comparisons others can contribute.

MAP sensor and pipe should be arriving tomorrow/thursday so I'll update. In the meantime still open to suggestions.

Thanks all.

 

New MAP sensor installed. No difference. I have also changed plugs, wires, fuel filter, battery. I tested the throttle position sensor and it seems OK. I disconnected the O2 sensor and nothing changed.When the engine dies the voltage at the coil dies. I ran a wire from the battery +ve to the coil +ve and ran the engine, the problem remained. So I still haven't decided if this is a fuel problem or a spark problem or a smec problem. I havea new coil on the way but other than throwing more new parts at it I'm fresh out of ideas.
The only thing that looks messed with is the wiring from the MAP sensor where one violet wire is soldered to 2 violet wires which I have written off as a damaged connector that was replaced with some solder, but I don't have another car to compare it with. Are there any wiring diagrams online? I have a haynes manual but it is very hard to comprehend the wiring diagram in there.

 

From the 1987 repair manual, 318 engine . Hope can help you. What happen with the new coil ?

 

wow, thank you so much for taking the time to help. Is there a page for the TBI fuel system? My car doesn't have a carb.
New coil in the mail should be here Monday or Tuesday. I am going to rebuild the throttle body tonight with new gaskets as apparently they can crack and cause a vacuum leak

 

Sorry it’s for 1987 carbureted 318 engine. I was going to think 1988 was the last year with carburetor and 1989 first year EFI.

 

Still not sure what the issue was here but it seems to be better now. I changed the throttle body to inlet manifold gasket (which was almost non existent having welded itself to the spacer) and also the 02 sensor. One of those solved the problem. The more I messed with it trying to fix this, the less frequent the problem became and I wonder if lack of use had mean the valves were not sealing quite right and a few good runs wore off some rust spots? Any how, I did a lot to it and it is running better now