need help quick!

[CraigWWW]

Hi

Please help!

Would love to have your opinions on this problem I am having..

Was away for a week just there and after gettin bak jumped in the Rex for a spin, took a few minutes to start (usually first turn) and then ran very lumpy for a while. Also car lost all power under light throttle a few times, felt like i had hit the brakes!!!

Once warmed up it seemed ok.

Later that day went out to do a bit of festive shopping and noticed that the digital mileage display was blank, backlight was on but no digits... and car started cutting out when i hit 2550rpm and when it reached 3600rpm, after a while the digits re-appeared and car ran normal.... exact same happened on way to work and back!!!! when the display works, the cars works?/

The car is standard, 65000miles and has been running not too bad recently... please would appreciate any ideas!!!

its a 1993, standard ecu...

Craig

[shaunwil]

How old is your battery Plus if you use a multimeter across the battery do you get about 14v when the car is running, if not your alternator is knackered !

Shaun

[CraigWWW]

Hi Shaun

Dont know the age of the battery, ive had the car for a year now and never chnaged it, chances are it could be old.

The voltmeter reads just over 14v when running...

any ideas im really stuck just now!!!

[Martiny]

Well it sounds like electrical problem, doesnt it?

Lets make sure your battery terminals are nice and clean, and tight. Then I suppose we need to make sure the earth going to the engine is good, too.

[shaunwil]

What voltage do you see across the battery when you start the car up ??

Shaun

[CraigWWW]

hi

Thanks for the response guys!

voltage across battery when running is 14.2V, ignition off is 12.4V.

I have checked the battery connections, as it lives in the boot its not corroded and the connections look new, shiny & tight...

How do i check the earth going to the engine?

[shaunwil]

oops i meant what is the voltage as you spin the starter motor ?? The engine is usually grounded to the body if you have your battery in the boot.

The other question is if you have thick enough cable running from your battery or a bad ground at the battery. Try moving the ground and seeing if it makes a difference.

Shaun

[CraigWWW]

I never took a note of the voltage on starting sorry.

the cable running to the battery seems really heavy duty stuff, although i dont know anything about electrics..

where can i find the ground?... there is a positive and a negative lead connected to battery and another thick cable that seems to be lying loose... should this be connected somewhere? Not sure if it ever was connected as someone has tapped the end up (either that or its broken off from a bodged connector)

sorry so vague but electrics baffle me....

[jetpilot]

Had a simialr problem on a boat once, alternator would be the thing i would be inclined to check!

[allstaruk]

I\'d be inclined to look for an earth fault to be honest

[Doofry]

Yeah sounds like an earth fault. If it was the alternator when it starts to cut out it would mean that it hadn\'t been charging enough for a while and had let the battery run down. If you stopped the engine at this point I wouldn\'t expect there to be enough current to crank the engine. This doesn\'t seem to be the case though and eitherway the car seems to quickly recover sometimes after nearly cutting out which wouldn\'t be consistent with the alternator. Also if the battery had almost discharged I\'d expect the injection/ignition to fail before the dash display totally disappeared.

If the engine is cranking okay when you start it (as it sounds like it is) then this should rule out there being an issue with the main earth connection to the chassis (usually to the engine but as you\'ve stated the battery has been relocated) and also the live route from the battery, ignition switch, starter relay and onto the starter motor. Alsoif you\'re getting 13.8v or more at the battery when the cars running it sounds like the alternator is okay. If the battery reading of around 12v was taken cold then sounds like that battery is also okay, plus if it\'s managing to crank the car for a while before starting then it also sounds good.

Sorry for the ramble but it gets us to the same point as before. Sounds like an earth problem....but not on the battery/main earth end but more shomewhere else on the loom. Did you notice anything else electrical acting up when the dash failed? You said the dash backlight seemed uneffected? I\'ve not liiked at an RX wiring diagram but possibley one could show where (logically) the dash electrics are earthed and whether it is seperate to that of the backlighing, etc.

Any of you guys familure with where the looms main earth points are? (i.e. behind the drivers side kick panel near relays, etc?). Is it also possible that it\'s an electronics or electronics earth problem as I\'m not sure what controls the odometer, is it controlled by the ecu or other black box? Possibly that is faulty or had a dodgy connection on a multiconnector, etc??

Sorry if this has been absolutely no help....just my 2p

[Doofry]

Just a thought but could there be a poor connection behind the clocks. Are the clocks internals responsable for sending signals back to the ecu regarding rpm, speed, etc? Just thought maybe if the multiconnector there was loose, etc. then maybe that would explain the dash cutting out and the engine running poorly. Maybe more likely is the speedo has been converted suggesting the clocks have been out to either fit a convertor or a new speedoface....hmmm?

[CraigWWW]

Thanks for taking time to have a think about it Doofry..

Having been xmas and all, not had the time I require to spend hunting for the problem, and still no fix.

I shall endevour to check all the earthing points,maybe a corroded connection or whatnot. Battery and alternator check out ok as you suggested.

The biggest puzzle is why the odemeter reading is somehow connected to the rpm/cutting out issue???

any ideas as to why these should be related?

forgot to mention... speedo/odemeter and odemeter stillas they were in Japan...

[Doofry]

Craig, I\'m just guessing as I don\'t know for sure how the RX7 electronics work but some of the other guys may be able to confirm or otherwise whether the speedo console internals are connected to the ECU to provide engine and car speed info as I mentioned above. From memory this is the case with the MR2 hence why when you fit a speed de-limited to patch one of the wires into one coming from the clocks to medify the car speed signal. If this is the case then the total lack of this connection (if say the clocks multiplug was loose) would surely have a dramatic effect on the ignition/injection? If this was the case then possibly the same mutiplug powers the clocks, etc.

As I said this is all purely speculation but it\'s not a biggy to pup the clocks out and check the connection and reseat it.

[CraigWWW]

It does sound like a logical point to start...

cheers mate!